Aquarium

   
A tropical display tank at the Georgia Aquarium

An aquarium (plural aquariums or aquaria) is a vivarium, usually contained in a clear-sided container (typically constructed of glass or high-strength plastic) in which water-dwelling plants and animals (usually fish, and sometimes invertebrates, as well as amphibians, marine mammals, and reptiles) are kept in captivity, often for public display; or it is an establishment featuring such displays. Aquarium keeping is a popular hobby around the world, with about 60 million enthusiasts worldwide. From the 1850s, when the predecessor of the modern aquarium was first developed as a novel curiosity, the ranks of aquarists have swelled as more sophisticated systems including lighting and filtration systems were developed to keep aquarium fish healthy. Public aquaria reproduce the home aquarist's hobby on a grand scale — the Osaka Aquarium, for example, boasts a tank of 5,400 m³ (1.4 million U.S. gallons) and a collection of about 580 species of aquatic life.

A wide variety of aquaria are now kept by hobbyists, ranging from a simple bowl housing a single fish to complex simulated ecosystems with carefully engineered support systems. Aquaria are usually classified as containing fresh or salt water, at tropical or cold water temperatures. These characteristics, and others, determine the type of fish and other inhabitants that can survive and thrive in the aquarium. Inhabitants for aquaria are often collected from the wild, although there is a growing list of organisms that are bred in captivity for supply to the aquarium trade.

The careful aquarist dedicates considerable effort to maintaining a tank ecology that mimics its inhabitants' natural habitat. Controlling water quality includes managing the inflow and outflow of nutrients, most notably the management of waste produced by tank inhabitants. The nitrogen cycle describes the flow of nitrogen from input via food, through toxic nitrogenous waste produced by tank inhabitants, to metabolism to less toxic compounds by beneficial bacteria populations. Other components in maintaining a suitable aquarium environment include appropriate species selection, management of biological loading, and good physical design.

South East Asian fish in the aquarium at Bristol Zoo, Bristol, England. The tank is about 2 metres (6 feet) high.

History and development

Etymology

The word aquarium itself is taken directly from the latin aqua, meaning water, with the suffix -rium, meaning "place" or "building".

Ancient practices

Koi have been kept in decorative ponds for centuries in China and Japan.

The keeping of fish in confined or artificial environments is a practice with deep roots in history. Ancient Sumerians were known to keep wild-caught fish in ponds, before preparing them for meals. In China, selective breeding of carp into today's popular koi and goldfish is believed to have begun over 2,000 years ago. Depictions of the sacred fish of Oxyrhynchus kept in captivity in rectangular temple pools have been found in ancient Egyptian art. Many other cultures also have a history of keeping fish for both functional and decorative purposes. The Chinese brought goldfish indoors during the Song dynasty to enjoy them in large ceramic vessels.

Glass enclosures

The concept of an aquarium, designed for the observation of fish in an enclosed, transparent tank to be kept indoors, emerged more recently. However, it is difficult to pinpoint the exact date of this development. In 1665 the diarist Samuel Pepys recorded seeing in London "a fine rarity, of fishes kept in a glass of water, that will live so forever, and finely marked they are, being foreign." The fish observed by Pepys were likely to have been the paradise fish, Macropodus opercularis, a familiar garden fish in Canton, China, where the East India Company was then trading. In the 18th century, the biologist Abraham Trembley kept hydra found in the garden canals of the Bentinck residence 'Sorgvliet' in the Netherlands, in large cylindrical glass vessels for study. The concept of keeping aquatic life in glass containers, then, dates to at latest this period.

Popularization

The keeping of fish in an aquarium first became a popular hobby in Britain only after ornate aquaria in cast-iron frames were featured at the Great Exhibition of 1851. The framed-glass aquarium was a specialized version of the glazed Wardian case developed for British horticulturists in the 1830s to protect exotic plants on long sea voyages. (One feature of some 19th-century aquaria that would prove curious to hobbyists today was the use of a metal base panel so that the aquarium water could be heated by flame.) Germans rivaled the British in their interest, and by the turn of the century Hamburg became the European port of entry for many newly seen species. Aquaria became more widely popular as houses became almost universally electrified after World War I. With electricity great improvements were made in aquarium technology, allowing artificial lighting as well as the aeration, filtration, and heating of the water. Popularization was also assisted by the availability of air freight, which allowed a much wider variety of fish to be successfully imported from distant regions of origin that consequently attracted new hobbyists.

There are currently estimated to be about 60 million aquarium hobbyists worldwide, and many more aquaria kept by them. The hobby has the strongest following in Europe, Asia, and North America. In the United States, a large minority (40%) of aquarists maintain two or more tanks at any one time.

Function and design

From the outdoor ponds and glass jars of antiquity, modern aquaria have evolved into a wide range of specialized systems. Aquaria can vary in size from a small bowl large enough for a single small fish, to the huge public aquaria that can simulate entire marine ecosystems. The most successful aquaria, as judged by the long-term survivability of its inhabitants, carefully emulate the natural environments that their residents would occupy in the wild.

Freshwater aquaria remain the most popular due to their lower cost and easier maintenance, but marine (saltwater) aquaria have gained cachet as dedicated enthusiasts prove it is possible to preserve these challenging environments.

Design

Filtration system in a typical aquarium: (1) Intake. (2) Mechanical filtration. (3) Chemical filtration. (4) Biological filtration medium. (5) Outflow to tank.

The common freshwater aquarium maintained by a home aquarist typically includes a filtration system, an artificial lighting system, air pumps, and a heater. In addition, some freshwater tanks (and most saltwater tanks) use powerheads to increase water circulation.

Combined biological and mechanical filtration systems are now common; these are designed to remove potentially dangerous build up of nitrogenous wastes and phosphates dissolved in the water, as well as particulate matter. Filtration systems are the most complexly engineered component of most home aquaria, and various designs are used. Most systems use pumps to remove a small portion of the tank's water to an external pathway where filtration occurs; the filtered water is then returned to the aquarium. Protein skimmers, filtration devices that remove proteins and other waste from the water, are usually found only in salt water aquaria.

Air pumps are employed to adequately oxygenate (or in the case of a heavily planted aquarium, provide carbon dioxide to) the water. These devices, once universal, are now somewhat less commonly used as some newer filtration systems create enough surface agitation to supply adequate gas exchange at the surface. Aquarium heaters are designed to act as thermostats to regulate water temperature at a level designated by the aquarist when the prevailing temperature of air surrounding the aquarium is below the desired water temperature. Coolers are also available for use in cold water aquaria or in parts of the world where the ambient room temperature is above the desired tank temperature.

An aquarium's physical characteristics form another aspect of aquarium design. Size, lighting conditions, density of floating and rooted plants, placement of bogwood, creation of caves or overhangs, type of substrate, and other factors (including an aquarium's positioning within a room) can all affect the behavior and survivability of tank inhabitants.

The combined function of these elements is to maintain appropriate water quality and characteristics suitable for the aquarium's residents.

Classifications

Aquaria can be classified by several variables that determine the type of aquatic life that can be suitably housed. The conditions and characteristics of the water contained in an aquarium are the most important classification criteria, as most aquatic life will not survive even limited exposure to unsuitable water conditions. The size of an aquarium also limits the aquarist in what types of ecosystems he can reproduce, species selection, and biological loading.

Water conditions

A saltwater aquarium

The dissolved content of water is perhaps the most important aspect of water conditions, as dissolved salts and other constituents can dramatically impact basic water chemistry, and therefore how organisms are able to interact with their environment. Salt content, or salinity, is the most basic classification of water conditions. An aquarium may have fresh water (a salt level of < 0.5%), simulating a lake or river environment; salt water (a salt level of 5%–18%), simulating an ocean or sea environment; or brackish water (a salt level of 0.5%–5%), simulating environments lying between fresh and salt, such as estuaries.

Several other water characteristics result from dissolved contents of the water, and are important to the proper simulation of natural environments. The pH of the water is a measure of alkalinity or acidity. Hardness measures overall dissolved mineral content; soft or hard water may be preferred. Dissolved organic content and dissolved gases content are also important factors.

Home aquarists typically use modified tap water supplied through their local municipal water system to fill their tanks. For freshwater aquaria, additives formulated to remove chlorine or chloramine (used to disinfect drinking water supplies for human consumption) are often all that is needed to make the water ready for aquarium use. Brackish or saltwater aquaria require the addition of a mixture of salts and other minerals, which are commercially available for this purpose. More sophisticated aquarists may make other modifications to their base water source to modify the water's alkalinity, hardness, or dissolved content of organics and gases, before adding it to their aquaria. In contrast, public aquaria with large water needs often locate themselves near a natural water source (such as a river, lake, or ocean) in order to have easy access to large volumes of water that does not require much further treatment.

Secondary water characteristics

Secondary water characteristics are also important to the success of an aquarium. The temperature of the water forms the basis of one of the two most basic aquarium classifications: tropical vs. cold water. Most fish and plant species tolerate only a limited range of water temperatures: Tropical or warm water aquaria, with an average temperature of about 25 °C (78 °F), are much more common and house most popular aquarium fish. Cold water aquaria are those with temperatures below what would be considered tropical; a variety of fish are better suited to this cooler environment.

Water movement can also be important in accurately simulating a natural ecosystem. Aquarists may prefer anything from still water up to swift simulated currents in an aquarium, depending on the conditions best suited for the aquarium's inhabitants.

Water temperature can be regulated with a combined thermometer/heater unit (or, more rarely, with a cooling unit), while water movement can be controlled through the use of powerheads and careful design of internal water flow (such as location of filtration system points of inflow and outflow).

Size

Simple hobbyist Aquarium, 80 x 30 x 40 cm, 96 liter

An aquarium can range from a small, unadorned glass bowl containing less than a liter of water – although generally unsuited for most fish (except, perhaps, air breathing fish such as Betta splendens or the Paradise Fish) – to massive tanks built in public aquaria which are limited only by engineering constraints and can house entire ecosystems as large as kelp forests or species of large sharks. In general, larger aquarium systems are typically recommended to hobbyists due to their resistance to rapid fluctuations of temperature and pH, allowing for greater system stability.

Aquaria kept in homes by hobbyists can be as small as 3 U.S. gallons (11 L). This size is widely considered the smallest practical system with filtration and other basic systems; indeed, the local government of Rome has recently taken the step of banning traditional goldfish bowls as inhumane. Practical limitations, most notably the weight (water weighs about 8.3 pounds per U.S. gallon (1 kg/L)) and internal water pressure (requiring thick, strong glass siding) of a large aquarium, keep most home aquaria to a maximum of around 1 m³ (300 U.S. gallons). However, some dedicated aquarists have been known to construct custom aquaria of up to several thousand U.S. gallons (several cubic meters), at great effort and expense.

Public aquaria designed for exhibition of large species or environments can be dramatically larger than any home aquarium. The Shedd Aquarium features an individual aquarium of two million U.S. gallons (7,500 m³), as well as two others of 400,000 U.S. gallons (1,500 m³). The Monterey Bay Aquarium has an acrylic viewing window into their largest tank. At 56 feet long by 17 feet high (17 by 5 m), it used to be the largest window in the world and is over 13 inches (330 mm) thick. The Okinawa Churaumi Aquarium is the world's second largest aquarium and part of the Ocean Expo Park located in Motobu, Okinawa. Its main tank, which holds 7,500 cubic meters of water, features the world's largest acrylic panel measuring 8.2 meters by 22.5 meters with a thickness of 60 centimeters. The size of public aquaria are usually limited by cost considerations.

Species selection

Several theories on species selection circulate within the community of hobby aquarists. Perhaps the most popular of these is the division of aquaria into either a community or aggressive tank type. Community tanks house several species that are not aggressive toward each other. This is the most common type of hobby aquarium kept today. Aggressive tanks, in contrast, house a limited number of species that can be aggressive toward other fish, or are able to withstand aggression well. In both of these tank types, the aquarium cohabitants may or may not originate from the same geographic region, but generally tolerate similar water conditions. In addition to the fish, invertebrates, plants, and decorations or "aquarium furniture" (all of which may or may not be natural neighbors of any of the fish) are typically added to these tank types.

Species or specimen tanks usually only house one fish species, along with plants, perhaps found in the fishes' natural environment and decorations simulating a true ecosystem. These tanks are often used for killifish, livebearers, cichlids etc. They can be simple as bare bottom with a few necessities or a complex planted aquarium. Some tanks of this sort are used simply to house adults for breeding. Such tanks are common in fishrooms, where people keep many tanks at home.

Ecotype or ecotope aquaria attempt to simulate a specific ecosystem found in the natural world, bringing together fish, invertebrate species, and plants found in that ecosystem in a tank with water conditions and decorations designed to simulate their natural environment. These ecotype aquaria might be considered the most sophisticated hobby aquaria; indeed, reputable public aquaria all use this approach in their exhibits whenever possible. This approach best simulates the experience of observing an aquarium's inhabitants in the wild, and also usually serves as the healthiest possible artificial environment for the tank's occupants.

Species selection for saltwater aquaria

In addition to the types above, a special category of saltwater aquaria is the reef aquarium. These aquaria attempt to simulate the complex reef ecosystems found in warm, tropical oceans around the world. These aquaria focus on the rich diversity of invertebrate life in these environments, and typically include only a limited number of small fish. Techniques of maintaining sea anemones, some corals, live rock, mollusks, and crustacea, developed since the 1980s, have made the recreations of a reef ecosystem possible. Reef aquaria are widely considered the most difficult and demanding of the common hobbyist aquarium types, requiring the most expertise in addition to the most specialized equipment (and corresponding high cost).

Source of aquarium inhabitants

A surface supplied diver interacts with viewers while feeding the fish

Fish and plants for the first modern aquaria were gathered from the wild and transported (usually by ship) to European and American ports. During the early twentieth century many species of small colorful tropical fish were caught and exported from Manaus Brazil, Bangkok Thailand, Siam, Jakarta Indonesia, the Dutch West Indies, Calcutta India, and other tropical ports. Collection of fish, plants, and invertebrates from the wild for supply to the aquarium trade continues today at locations around the world. In many places of the world, impoverished local villagers collect specimens for the aquarium trade as their prime means of income. It remains an important source for many species that have not been successfully bred in captivity, and continues to introduce new species to enthusiastic aquarists.

The practice of collection in the wild for eventual display in aquaria has several disadvantages. Collecting expeditions can be lengthy and costly, and are not always successful. The shipping process is very hazardous for the fish involved; mortality rates are high. Many others are weakened by stress and become diseased upon arrival. Fish can also be injured during the collection process itself, most notably during the process of using cyanide to stun reef fish to make them easier to collect.

More recently, the potentially detrimental environmental impact of fish and plant collecting has come to the attention of aquarists worldwide. These include the poisoning of coral reefs and non-target species, the depletion of rare species from their natural habitat, and the degradation of ecosystems from large scale removal of key species. Additionally, the destructive fishing techniques used have become a growing concern to environmentalists and hobbyists alike. Therefore, there has been a concerted movement by many concerned aquarists to reduce the trade's dependence on wild-collected specimens through captive breeding programs and certification programs for wild-caught fish. Among American keepers of marine aquaria surveyed in 1997, two thirds said that they prefer to purchase farm raised coral instead of wild-collected coral, and over 80% think that only sustainably caught or captive bred fish should be allowed for trade.

Since the 'fighting fish' Betta splendens was first successfully bred in France in 1893, captive spawning techniques have been slowly discovered. Captive breeding for the aquarium trade is now concentrated in South Florida, Singapore, Hong Kong, and Bangkok, with smaller industries in Hawaii and Sri Lanka. Captive breeding programs of marine organisms for the aquarium trade have been urgently in development since the mid-1990s. Breeding programs for freshwater species are comparatively more advanced than for saltwater species.

Aquaculture is the cultivation of aquatic organisms in a controlled environment. Supporters of aquaculture programs for supply to the aquarium trade claim that well-planned programs can bring benefits to the environment as well as the society around it. Aquaculture can help in lessening the impacts on wild stocks, either by using raised cultivated organisms directly for sale or by releasing them to replenish wild stock (Tlusty 203), although such a practice is associated with several environmental risks.

Ecology

Ideal aquarium ecology reproduces the equilibrium found in nature in the closed system of an aquarium. In practice it is virtually impossible to maintain a perfect balance. As an example, a balanced predator-prey relationship is nearly impossible to maintain in even the largest of aquaria. Typically an aquarium keeper must take steps to maintain equilibrium in the small ecosystem contained in his aquarium.

Approximate equilibrium is facilitated by large volumes of water. Any event that perturbs the system pushes an aquarium away from equilibrium; the more water that is contained in a tank, the easier such a systemic shock is to absorb, as the effects of that event are diluted. For example, the death of the only fish in a three U.S. gallon tank (11 L) causes dramatic changes in the system, while the death of that same fish in a 100 U.S. gallon (400 L) tank with many other fish in it represents only a minor change in the balance of the tank. For this reason, hobbyists often favor larger tanks when possible, as they are more stable systems requiring less intensive attention to the maintenance of equilibrium.

Nitrogen cycle

The nitrogen cycle in an aquarium.

Of primary concern to the aquarist is management of the biological waste produced by an aquarium's inhabitants. Fish, invertebrates, fungi, and some bacteria excrete nitrogen waste in the form of ammonia (which may convert to ammonium, depending on water chemistry) which must then pass through the nitrogen cycle. Ammonia is also produced through the decomposition of plant and animal matter, including fecal matter and other detritus. Nitrogen waste products become toxic to fish and other aquarium inhabitants at high concentrations.

A well-balanced tank contains organisms that are able to metabolize the waste products of other aquarium residents. The nitrogen waste produced in a tank is metabolized in aquaria by a type of bacteria known as nitrifiers (genus Nitrosomonas). Nitrifying bacteria capture ammonia from the water and metabolize it to produce nitrite. Nitrite is also highly toxic to fish in high concentrations. Another type of bacteria, genus Nitrospira, converts nitrite into nitrate, a less toxic substance to aquarium inhabitants. (Nitrobacter bacteria were previously believed to fill this role, and continue to be found in commercially available products sold as kits to "jump start" the nitrogen cycle in an aquarium. While biologically they could theoretically fill the same niche as Nitrospira, it has recently been found that Nitrobacter are not present in detectable levels in established aquaria, while Nitrospira are plentiful.) This process is known in the aquarium hobby as the nitrogen cycle.

In addition to bacteria, aquatic plants also eliminate nitrogen waste by metabolizing ammonia and nitrate. When plants metabolize nitrogen compounds, they remove nitrogen from the water by using it to build biomass. However, this is only temporary, as the plants release nitrogen back into the water when older leaves die off and decompose.

Although informally called the nitrogen cycle by hobbyists, it is in fact only a portion of a true cycle: nitrogen must be added to the system (usually through food provided to the tank inhabitants), and nitrates accumulate in the water at the end of the process (or contribute to a growth in biomass via plant metabolism). This accumulation of nitrates in home aquaria requires the aquarium keeper to remove water that is high in nitrates or remove plants which have grown from the nitrates. A balanced system, in which the fish eat the plants, is generally difficult to create.

Aquaria kept by hobbyists often do not have the requisite populations of bacteria needed to detoxify nitrogen waste from tank inhabitants. This problem is most often addressed through two filtration solutions: Activated carbon filters absorb nitrogen compounds and other toxins from the water, while biological filters provide a medium specially designed for colonization by the desired nitrifying bacteria.

Cycling

New aquaria also do not usually have the required populations of bacteria for the handling of nitrogen waste. In a process called cycling, aquarists cultivate these bacteria as fish and other producers of nitrogen waste are gradually added to the tank over the course of several weeks. Aquarists use several different methods to jump start this process, including the use of water additives containing small populations of the bacteria, or "seeding" a new tank with a mature bacterial colony removed from another aquarium (such as can be found on gravel or biological filter media).

Other cycling methods that have gained popularity in recent years are the fishless cycle and the silent cycle. As the name of the former implies, no fish are kept in a tank undergoing a fishless cycle. Instead, small amounts of ammonia are added to the tank to feed the bacteria being cultured. During this process, ammonia, nitrite, and nitrate levels are tested to monitor progress. The silent cycle is basically nothing more than densely stocking the aquarium with fast-growing aquatic plants and relying on them to consume the nitrogen products rather than bacteria. According to anecdotal reports of aquarists specializing in planted tanks, the plants can consume nitrogenous waste so efficiently that the spikes in ammonia and nitrite levels normally seen in more traditional cycling methods are greatly reduced, if they are detectable at all.

Improperly cycled aquaria can quickly accumulate toxic concentrations of nitrogen waste and kill its inhabitants.

Other nutrient cycles

Nitrogen is not the only nutrient that cycles through an aquarium. Dissolved oxygen enters the system at the surface water-air interface or through the actions of an air pump. Carbon dioxide escapes the system into the air. The phosphate cycle is an important, although often overlooked, nutrient cycle. Sulfur, iron, and micronutrients also cycle through the system, entering as food and exiting as waste. Appropriate handling of the nitrogen cycle, along with supplying an adequately balanced food supply and considered biological loading, is usually enough to keep these other nutrient cycles in approximate equilibrium.

Biological loading

Biological loading is a measure of the burden placed on the aquarium ecosystem by its living inhabitants. High biological loading in an aquarium represents a more complicated tank ecology, which in turn means that equilibrium is easier to perturb. In addition, there are several fundamental constraints on biological loading based on the size of an aquarium. The surface area of water exposed to air limits dissolved oxygen intake by the tank. The capacity of nitrifying bacteria is limited by the physical space they have available to colonize. Physically, only a limited size and number of plants and animals can be fit into an aquarium while still providing room for movement.

In order to prevent biological overloading of the system, aquarists have developed a number of rules of thumb. Perhaps the most popular of these is the "one inch of fish per U.S. gallon" rule, which dictates that the sum in inches of the lengths of all fish kept in an aquarium (excluding tail length) should not exceed the capacity of the tank measured in U.S. gallons (about 7 mm per liter of water). This rule is usually applied to the expected mature size of the fish, in order to not stunt growth by overcrowding, which can be unhealthy for the fish. For goldfish and other high-waste fish, some aquarists recommend doubling the space allowance to one inch of fish per every two gallons.

The true maximum or ideal biological loading of a system is very difficult to calculate, even on a theoretical level. To do so, the variables for waste production rate, nitrification efficiency, gas exchange rate at the water surface, and many others would need to be determined. In practice this is a very complicated and difficult task, and so most aquarists use rules of thumb combined with a trial and error approach to reach an appropriate level of biological loading.

Public aquaria

A 335,000 U.S. gallon (1.3 million liter) aquarium at the Monterey Bay Aquarium in California displaying a simulated kelp forest ecosystem

Public aquaria are facilities open to the public for viewing of aquatic species in aquaria. Most public aquaria feature a number of smaller tanks, as well as one or more large tank greater in size than could be kept by any home aquarist. The largest tanks hold millions of U.S. gallons of water and can house large species, including dolphins, sharks or beluga whales. Aquatic and semiaquatic animals, including otters and penguins, may also be kept by public aquaria.

Operationally, a public aquarium is similar in many ways to a zoo or museum. A good aquarium will have special exhibits to entice repeat visitors, in addition to its permanent collection. A few have their own version of a "petting zoo"; for instance, the Monterey Bay Aquarium has a shallow tank filled with common types of rays, and one can reach in to feel their leathery skins as they pass by.

Also as with zoos, aquaria usually have specialized research staff who study the habits and biology of their specimens. In recent years, the large aquaria have been attempting to acquire and raise various species of open-ocean fish, and even jellyfish (or sea-jellies, cnidaria), a difficult task since these creatures have never before encountered solid surfaces like the walls of a tank, and do not have the instincts to turn aside from the walls instead of running into them.

The first public aquarium opened in London's Regent's Park in 1853. P.T. Barnum quickly followed with the first American aquarium, opened on Broadway in New York. Following early examples of Detroit, New York and San Francisco, many major cities now have public aquaria. Most public aquaria are located close to the ocean, for a steady supply of natural seawater. An inland pioneer was Chicago's Shedd Aquarium that received seawater shipped by rail in special tank cars. In contrast, the recently opened Georgia Aquarium filled its tanks with fresh water from the city water system and salinated its salt water exhibits using the same commercial salt and mineral additives available to home aquarists.

In January 1985 Kelly Tarlton began construction of the first aquarium to include a large transparent acrylic tunnel in Auckland, New Zealand, a task that took 10 months and cost NZ$3 million. The 110-meter tunnel was built from one-tonne slabs of German sheet plastic that were shaped locally in an oven. A moving walkway now transports visitors through, and groups of school children occasionally hold sleepovers there beneath the swimming sharks and rays.

Top public aquaria are often affiliated with important oceanographic research institutions or conduct their own research programs, and usually (though not always) specialize in species and ecosystems that can be found in local waters.

For a partial list of public aquaria worldwide, see list of aquaria.


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For a partial list of public aquaria worldwide, see list of aquaria. Frog fossils have been found on all continents, including Antarctica. Top public aquaria are often affiliated with important oceanographic research institutions or conduct their own research programs, and usually (though not always) specialize in species and ecosystems that can be found in local waters. The main evolutionary changes involved shortening of the body and loss of the tail. A moving walkway now transports visitors through, and groups of school children occasionally hold sleepovers there beneath the swimming sharks and rays. It seems likely that the evolution of modern anura was completed by the Jurassic period. The 110-meter tunnel was built from one-tonne slabs of German sheet plastic that were shaped locally in an oven. †Notobatrachus degiustoi from the Middle Jurassic is just a bit younger, about 155-170 million years old.

In January 1985 Kelly Tarlton began construction of the first aquarium to include a large transparent acrylic tunnel in Auckland, New Zealand, a task that took 10 months and cost NZ$3 million. It is known only from the dorsal and ventral impressions of a single animal and was estimated to be 33 mm in snout-vent length. In contrast, the recently opened Georgia Aquarium filled its tanks with fresh water from the city water system and salinated its salt water exhibits using the same commercial salt and mineral additives available to home aquarists. The earliest true frog is †Vieraella herbsti, from the Early Jurassic (188-213 mya). An inland pioneer was Chicago's Shedd Aquarium that received seawater shipped by rail in special tank cars. Unlike Triadobatrachus, Prosalirus had already lost nearly all of its tail. Most public aquaria are located close to the ocean, for a steady supply of natural seawater. Like Triadobatrachus, Prosalirus did not have greatly enlarged legs, but possessed the typical three-pronged pelvic structure.

Following early examples of Detroit, New York and San Francisco, many major cities now have public aquaria. Another fossil frog, discovered in Arizona and called Prosalirus bitis, was uncovered in 1985, and dates from roughly the same time as Triadobatrachus. Barnum quickly followed with the first American aquarium, opened on Broadway in New York. The tibia and fibula bones are unfused and separate, making it probable that Triadobatrachus was not a very efficient leaper. P.T. These include a different ilium, a longer body with more vertebrae, the lack of a urostyle and vertebrae in its tail. The first public aquarium opened in London's Regent's Park in 1853. The skull is frog-like being broad with large eye sockets, but the fossil has a number of other features differing to modern amphibia.

In recent years, the large aquaria have been attempting to acquire and raise various species of open-ocean fish, and even jellyfish (or sea-jellies, cnidaria), a difficult task since these creatures have never before encountered solid surfaces like the walls of a tank, and do not have the instincts to turn aside from the walls instead of running into them. It is about 250 million years old, and had not yet evolved the full combination of features currently being associated with frogs. Also as with zoos, aquaria usually have specialized research staff who study the habits and biology of their specimens. The earliest known (proto)frog is †Triadobatrachus massinoti, from the Early Triassic of Madagascar. A few have their own version of a "petting zoo"; for instance, the Monterey Bay Aquarium has a shallow tank filled with common types of rays, and one can reach in to feel their leathery skins as they pass by. Suggestions include the lung-fish and the Actinopterygii as the forerunners to modern amphibia. A good aquarium will have special exhibits to entice repeat visitors, in addition to its permanent collection. There is however, substantial debate over what type of bony fish was the amphibian precursor.

Operationally, a public aquarium is similar in many ways to a zoo or museum. These first amphibians are thought to have evolved from bony fish of the Class Osteichthyes which was widespread during the period that amphibia emerged. Aquatic and semiaquatic animals, including otters and penguins, may also be kept by public aquaria. The later Paleozoic saw a great diversity of amphibians, ranging from small legless swimming forms (Aïstopoda) to bizarre "horned" forms (Nectridea). gallons of water and can house large species, including dolphins, sharks or beluga whales. The earliest amphibian discovered to date is Elginerpeton, found in Late Devonian rocks of Scotland dating to approximately 368 million years ago. The largest tanks hold millions of U.S. The earliest well-known amphibian, Ichthyostega, was found in Late Devonian deposits in Greenland, dating back about 363 million years.

Most public aquaria feature a number of smaller tanks, as well as one or more large tank greater in size than could be kept by any home aquarist. Bombina bombina and Bombina variegata similarly form hybrids, although these are less fertile, giving rise to a hybrid zone. Public aquaria are facilities open to the public for viewing of aquatic species in aquaria. ridibunda). In practice this is a very complicated and difficult task, and so most aquarists use rules of thumb combined with a trial and error approach to reach an appropriate level of biological loading. lessonae) and the Marsh Frog (R. To do so, the variables for waste production rate, nitrification efficiency, gas exchange rate at the water surface, and many others would need to be determined. For instance, the Edible Frog (Rana esculenta) is a hybrid of the Pool Frog (R.

The true maximum or ideal biological loading of a system is very difficult to calculate, even on a theoretical level. Many Anurans readily hybridise. For goldfish and other high-waste fish, some aquarists recommend doubling the space allowance to one inch of fish per every two gallons. The distinction is far from universally accepted, especially because there are few features that are as unique to any group as taxonomists would like. This rule is usually applied to the expected mature size of the fish, in order to not stunt growth by overcrowding, which can be unhealthy for the fish. This classification is based on the perceived possession of derived features of the three groups and refers to a fairly deep phylogenetic split, with the newest group, the Neobatrachia, having some 5,000 species. gallons (about 7 mm per liter of water). Frogs and toads are broadly classified into three suborders: Archaeobatrachia, Mesobatrachia and Neobatrachia - respectively, old, intermediate and new frogs.

gallon" rule, which dictates that the sum in inches of the lengths of all fish kept in an aquarium (excluding tail length) should not exceed the capacity of the tank measured in U.S. While its skin is slightly warty, it prefers a watery habitat. Perhaps the most popular of these is the "one inch of fish per U.S. An exception can be made for the Fire-bellied toad (Bombina bombina). In order to prevent biological overloading of the system, aquarists have developed a number of rules of thumb. The distinction between frogs and toads is usually based on the ability to retain moisture; frogs are smooth and moist skinned, while toads have dry, warty skin. Physically, only a limited size and number of plants and animals can be fit into an aquarium while still providing room for movement. However, many families, and even genera, have a mixture of frogs and toads, so there is no taxonomic justification.

The capacity of nitrifying bacteria is limited by the physical space they have available to colonize. Most frogs in the Ranidae family (true frogs) and Hylidae family (tree frogs) are considered frogs, whereas all those within the Bufonidae family (true toads) are considered toads. The surface area of water exposed to air limits dissolved oxygen intake by the tank. This distinction has no scientific basis, and only refers to the common name of a species. In addition, there are several fundamental constraints on biological loading based on the size of an aquarium. A problem commonly associated with Anurans is the distinction between frogs and toads. High biological loading in an aquarium represents a more complicated tank ecology, which in turn means that equilibrium is easier to perturb. The order Anura contains some 5250 species in 33 families, whereof the Leptodactylidae (1100 spp.), Hylidae (800 spp.) and Ranidae (750 spp.) are the most speciose.

Biological loading is a measure of the burden placed on the aquarium ecosystem by its living inhabitants. Although habitat loss is certainly one of the most important features of most declines; pollutants, climate change, introduction of non-indigenous predators/competitors, and infectious diseases (see Chytrid fungus) have also been implicated. Appropriate handling of the nitrogen cycle, along with supplying an adequately balanced food supply and considered biological loading, is usually enough to keep these other nutrient cycles in approximate equilibrium. The decline in frog diversity may also be to do with particular species having specialised on particular kinds of prey, such as certain kinds of earthworms that are themselves indicator species due to their close dependence on soil chemistry. Sulfur, iron, and micronutrients also cycle through the system, entering as food and exiting as waste. Many environmental scientists feel that amphibians, and frogs in particular, may be excellent biological indicators of ecosystem function because of their location on the food web, their permeable skins and their typically bi-phasic life (in both water and on land). The phosphate cycle is an important, although often overlooked, nutrient cycle. In many parts of the world, the frog populations have declined drastically since the 1950s.

Carbon dioxide escapes the system into the air. Frogs are found nearly worldwide, but they do not occur in Antarctica and are not present on many oceanic islands. Dissolved oxygen enters the system at the surface water-air interface or through the actions of an air pump. Darwin's Frog (Rhinoderma darwinii) from Chile puts the tadpoles in its vocal sac for development. Nitrogen is not the only nutrient that cycles through an aquarium. To do this, the Gastric-brooding Frog must stop secreting stomach acid and suppress peristalsis (contractions of the stomach). Improperly cycled aquaria can quickly accumulate toxic concentrations of nitrogen waste and kill its inhabitants. The female Gastric-brooding Frogs (genus: Rheobatrachus) from Australia swallows its tadpoles which develop in the stomach.

According to anecdotal reports of aquarists specializing in planted tanks, the plants can consume nitrogenous waste so efficiently that the spikes in ammonia and nitrite levels normally seen in more traditional cycling methods are greatly reduced, if they are detectable at all. The tadpoles will reside in the pouch until the end of metamorphosis. The silent cycle is basically nothing more than densely stocking the aquarium with fast-growing aquatic plants and relying on them to consume the nitrogen products rather than bacteria. The male Australian pouched frog (Assa darlingtoni) has pouches along its side. During this process, ammonia, nitrite, and nitrate levels are tested to monitor progress. Many frogs protect their offspring inside their own body. Instead, small amounts of ammonia are added to the tank to feed the bacteria being cultured. the midwife toads, Alytes spp.).

As the name of the former implies, no fish are kept in a tank undergoing a fishless cycle. Other frogs will carry the eggs and tadpoles on their hind legs or back (e.g. Other cycling methods that have gained popularity in recent years are the fishless cycle and the silent cycle. The parent will then feed it through laying unfertilised eggs into the bromeliad, until the young have metamorphosed. Aquarists use several different methods to jump start this process, including the use of water additives containing small populations of the bacteria, or "seeding" a new tank with a mature bacterial colony removed from another aquarium (such as can be found on gravel or biological filter media). After hatching, a parent (sex depending upon the species) will move them, on its back, to a water-holding bromeliad. In a process called cycling, aquarists cultivate these bacteria as fish and other producers of nitrogen waste are gradually added to the tank over the course of several weeks. The frog will urinate if they become too dry.

New aquaria also do not usually have the required populations of bacteria for the handling of nitrogen waste. This protection involves guarding the eggs from predation, and keeping the eggs moist. This problem is most often addressed through two filtration solutions: Activated carbon filters absorb nitrogen compounds and other toxins from the water, while biological filters provide a medium specially designed for colonization by the desired nitrifying bacteria. Some species of poison dart frogs will lay eggs on the forest floor, and protect them until hatching. Aquaria kept by hobbyists often do not have the requisite populations of bacteria needed to detoxify nitrogen waste from tank inhabitants. Although brood care is much less common, there is a great diversity of such behaviours. A balanced system, in which the fish eat the plants, is generally difficult to create. This reduces the number of predators, and therefore increases the number of surviving offspring.

This accumulation of nitrates in home aquaria requires the aquarium keeper to remove water that is high in nitrates or remove plants which have grown from the nitrates. They will lay the eggs en masse, and any predator within the region will die once they eat the egg or tadpole. Although informally called the nitrogen cycle by hobbyists, it is in fact only a portion of a true cycle: nitrogen must be added to the system (usually through food provided to the tank inhabitants), and nitrates accumulate in the water at the end of the process (or contribute to a growth in biomass via plant metabolism). Although the Cane Toad, and similar species, do not advertise their toxicity the offspring still survive in large numbers. However, this is only temporary, as the plants release nitrogen back into the water when older leaves die off and decompose. Other poisonous species will not, such as the Cane Toad (Bufo marinus). When plants metabolize nitrogen compounds, they remove nitrogen from the water by using it to build biomass. Some tadpoles will advertise their toxicity, usually poison dart frogs, to warn potential prey.

In addition to bacteria, aquatic plants also eliminate nitrogen waste by metabolizing ammonia and nitrate. Poisonous tadpoles and/or eggs is an adaptation also present in frogs. While biologically they could theoretically fill the same niche as Nitrospira, it has recently been found that Nitrobacter are not present in detectable levels in established aquaria, while Nitrospira are plentiful.) This process is known in the aquarium hobby as the nitrogen cycle. The tadpoles drop into the water upon hatching. (Nitrobacter bacteria were previously believed to fill this role, and continue to be found in commercially available products sold as kits to "jump start" the nitrogen cycle in an aquarium. One way in which some species avoid the predation and pathogens eggs are exposed to in ponds is to lay eggs on leaves above the pond, with a coating designed to retain moisture. Another type of bacteria, genus Nitrospira, converts nitrite into nitrate, a less toxic substance to aquarium inhabitants. However, there is a greater chance some will survive than a laying of smaller numbers.

Nitrite is also highly toxic to fish in high concentrations. A majority of the offspring will usually die due to predation, disease or competition with other tadpoles. Nitrifying bacteria capture ammonia from the water and metabolize it to produce nitrite. The female will lay thousands of eggs in one laying. The nitrogen waste produced in a tank is metabolized in aquaria by a type of bacteria known as nitrifiers (genus Nitrosomonas). The most common adaptation is mass laying of eggs. A well-balanced tank contains organisms that are able to metabolize the waste products of other aquarium residents. Frogs have evolved many techniques to protect the survival of the next generation.

Nitrogen waste products become toxic to fish and other aquarium inhabitants at high concentrations. The egg and tadpole stage of a frog's life cycle is usually the most dangerous due to easy predation. Ammonia is also produced through the decomposition of plant and animal matter, including fecal matter and other detritus. More importantly, reproducing early in the season ensures that appropriate food is available to the developing frogs at the right time. Fish, invertebrates, fungi, and some bacteria excrete nitrogen waste in the form of ammonia (which may convert to ammonium, depending on water chemistry) which must then pass through the nitrogen cycle. Reproducing in these conditions helps the developing tadpoles because dissolved oxygen concentrations in the water are highest at cold temperatures. Of primary concern to the aquarist is management of the biological waste produced by an aquarium's inhabitants. Water temperatures at this time of year are relatively low and typically between four and 10 degrees Celsius.

For this reason, hobbyists often favor larger tanks when possible, as they are more stable systems requiring less intensive attention to the maintenance of equilibrium. In the UK most common frog populations produce frogspawn in February although there is wide variation in timing. gallon (400 L) tank with many other fish in it represents only a minor change in the balance of the tank. Most temperate species of frog reproduce in the period between late autumn to early spring. gallon tank (11 L) causes dramatic changes in the system, while the death of that same fish in a 100 U.S. The eggs will hatch after a short time, releasing tadpoles. For example, the death of the only fish in a three U.S. The eggs are typically brown or black, with a clear, gelatine-like, covering.

Any event that perturbs the system pushes an aquarium away from equilibrium; the more water that is contained in a tank, the easier such a systemic shock is to absorb, as the effects of that event are diluted. Once the eggs come in contact with the water, they will swell, and form a protective coating. Approximate equilibrium is facilitated by large volumes of water. The female then releases her eggs, which the male frog covers with a sperm solution before the eggs make contact with the water. Typically an aquarium keeper must take steps to maintain equilibrium in the small ecosystem contained in his aquarium. This involves the male mounting the female and gripping her tightly. As an example, a balanced predator-prey relationship is nearly impossible to maintain in even the largest of aquaria. The male and female frog, will then undergo amplexus.

In practice it is virtually impossible to maintain a perfect balance. Some species have satellite males who do not call but intercept females approaching one of the calling males. Ideal aquarium ecology reproduces the equilibrium found in nature in the closed system of an aquarium. The call is unique to the species, and will attract females of that species. Aquaculture can help in lessening the impacts on wild stocks, either by using raised cultivated organisms directly for sale or by releasing them to replenish wild stock (Tlusty 203), although such a practice is associated with several environmental risks. They will then call, collectively becoming a chorus of frogs. Supporters of aquaculture programs for supply to the aquarium trade claim that well-planned programs can bring benefits to the environment as well as the society around it. The life cycle continues with male frogs of a species assembling at a still water source.

Aquaculture is the cultivation of aquatic organisms in a controlled environment. The French custom of eating frog legs is the source of the English use of the derogatory nickname "frogs" for French people. Breeding programs for freshwater species are comparatively more advanced than for saltwater species. Frog legs are a delicacy in China, France, and in many parts of the American South, especially Louisiana. Captive breeding programs of marine organisms for the aquarium trade have been urgently in development since the mid-1990s. Frogs are also eaten by people. Captive breeding for the aquarium trade is now concentrated in South Florida, Singapore, Hong Kong, and Bangkok, with smaller industries in Hawaii and Sri Lanka. Frogs are themselves predated by birds, large fish, snakes, otters, foxes, badgers, coatis, and other animals.

Since the 'fighting fish' Betta splendens was first successfully bred in France in 1893, captive spawning techniques have been slowly discovered. Some frogs use their sticky tongues effectively in catching fast-moving prey, while others capture their prey, and force it into their mouth with their hands. Among American keepers of marine aquaria surveyed in 1997, two thirds said that they prefer to purchase farm raised coral instead of wild-collected coral, and over 80% think that only sustainably caught or captive bred fish should be allowed for trade. A few of the larger species may eat larger prey, such as small mammals, fish and smaller frogs. Therefore, there has been a concerted movement by many concerned aquarists to reduce the trade's dependence on wild-collected specimens through captive breeding programs and certification programs for wild-caught fish. All juvenile and adult frogs are carnivores, eating invertebrates such as insects, worms and spiders. Additionally, the destructive fishing techniques used have become a growing concern to environmentalists and hobbyists alike. Most species complete their development within about three months, while others, such as the midwife toad Alytes obstetricans and the Common Spadefoot (Pelobates fuscus), hibernate as tadpoles and complete their development the following spring.

These include the poisoning of coral reefs and non-target species, the depletion of rare species from their natural habitat, and the degradation of ecosystems from large scale removal of key species. The final stage of development from froglet to adult frog involves apoptosis (programmed cell death) of the tail. More recently, the potentially detrimental environmental impact of fish and plant collecting has come to the attention of aquarists worldwide. As tadpoles grow, they undergo metamorphosis, in which they develop legs and lungs, have their intestines shorten to accommodate a carnivorous diet, to become a froglet. Fish can also be injured during the collection process itself, most notably during the process of using cyanide to stun reef fish to make them easier to collect. Cannibalism has also been observed among tadpoles. Many others are weakened by stress and become diseased upon arrival. Tadpoles are entirely aquatic, and are vulnerable to predation by fish, newts, predatory diving beetles, and birds such as kingfishers.

The shipping process is very hazardous for the fish involved; mortality rates are high. Some species are carnivorous at the tadpole stage, usually eating small larvae and fish. Collecting expeditions can be lengthy and costly, and are not always successful. Tadpoles are typically herbivorous, feeding mostly on algae, including diatoms that are filtered from the water through the gills. The practice of collection in the wild for eventual display in aquaria has several disadvantages. Frogs start life as tadpoles. It remains an important source for many species that have not been successfully bred in captivity, and continues to introduce new species to enthusiastic aquarists. The life cycle of frogs contains two main stages, the adult and the tadpole.

In many places of the world, impoverished local villagers collect specimens for the aquarium trade as their prime means of income. Edible frogs rely on skin modifications rather than poisons for protection. Collection of fish, plants, and invertebrates from the wild for supply to the aquarium trade continues today at locations around the world. There is also one nonpoisonous frog in South America which mimics a poisonous frog’s colors to protect itself. During the early twentieth century many species of small colorful tropical fish were caught and exported from Manaus Brazil, Bangkok Thailand, Siam, Jakarta Indonesia, the Dutch West Indies, Calcutta India, and other tropical ports. Poisonous frogs tend to advertise their toxicity with bright colours. Fish and plants for the first modern aquaria were gathered from the wild and transported (usually by ship) to European and American ports. The name of the frog was changed from Poison Arrow Frog to Poison Dart Frog in the early 1980's.

Reef aquaria are widely considered the most difficult and demanding of the common hobbyist aquarium types, requiring the most expertise in addition to the most specialized equipment (and corresponding high cost). It was previously a misconception that the poison was placed on arrows rather than darts. Techniques of maintaining sea anemones, some corals, live rock, mollusks, and crustacea, developed since the 1980s, have made the recreations of a reef ecosystem possible. Some natives of the Amazon area extract poison from the Poison Dart Frog and put it on their darts when hunting. These aquaria focus on the rich diversity of invertebrate life in these environments, and typically include only a limited number of small fish. The Australian Corroboree Frogs, Pseudophryne corroboree and Pseudophryne pengilleyi, have been discovered to be able to manufacture an alkaloid not derived from their diet [2]. These aquaria attempt to simulate the complex reef ecosystems found in warm, tropical oceans around the world. Generally the frog obtains the poison from the insects and other animals it eats.

In addition to the types above, a special category of saltwater aquaria is the reef aquarium. Many predators of frogs have adapted to tolerate high levels of these poisons, whereas others, including humans, may be severely affected and hence deterred by them. This approach best simulates the experience of observing an aquarium's inhabitants in the wild, and also usually serves as the healthiest possible artificial environment for the tank's occupants. The chemical makeup of these toxins varies from irritants to hallucinogens, convulsants, nerve poisons, and vasoconstrictors (which act to narrow the blood vessels). These ecotype aquaria might be considered the most sophisticated hobby aquaria; indeed, reputable public aquaria all use this approach in their exhibits whenever possible. Some frogs, such as the arrow-poison frog, are especially toxic. Ecotype or ecotope aquaria attempt to simulate a specific ecosystem found in the natural world, bringing together fish, invertebrate species, and plants found in that ecosystem in a tank with water conditions and decorations designed to simulate their natural environment. All frogs have poison glands in their skin.

Such tanks are common in fishrooms, where people keep many tanks at home. Certain frogs change colour between night and day, which is caused by light and moisture stimulating the pigment cells and causing them to expand or contract. Some tanks of this sort are used simply to house adults for breeding. Arboreal frogs will usually have smooth skin to effectively disguise them as leaves. They can be simple as bare bottom with a few necessities or a complex planted aquarium. Features such as warts or skin folds are usually found on ground dwelling frogs, where a smooth skin would not disguise them effectively. These tanks are often used for killifish, livebearers, cichlids etc. For example, White's tree frog (Litoria caerulea) varies in shades of green and brown.

Species or specimen tanks usually only house one fish species, along with plants, perhaps found in the fishes' natural environment and decorations simulating a true ecosystem. However, this is usually restricted to shades of one or two colours. In addition to the fish, invertebrates, plants, and decorations or "aquarium furniture" (all of which may or may not be natural neighbors of any of the fish) are typically added to these tank types. Some frogs have the ability to change colour. In both of these tank types, the aquarium cohabitants may or may not originate from the same geographic region, but generally tolerate similar water conditions. Nocturnal frogs will usually find the ideal camouflaged position during the day to sleep. Aggressive tanks, in contrast, house a limited number of species that can be aggressive toward other fish, or are able to withstand aggression well. Most camouflaged frogs are nocturnal, which adds to their ability to hide.

This is the most common type of hobby aquarium kept today. Camouflage is a common defensive mechanism in frogs. Community tanks house several species that are not aggressive toward each other. They can also breathe with their mouths closed by taking air in through the nostrils (causing the throat to puff out), and then compressing the floor of the mouth, which forces the air into the lungs. Perhaps the most popular of these is the division of aquaria into either a community or aggressive tank type. Frogs can breathe by simply opening their mouth and letting air flow into their windpipe. Several theories on species selection circulate within the community of hobby aquarists. Their lungs are similar to those of humans, but the chest muscles are not involved in respiration and there are no ribs or diaphragm to support breathing.

The size of public aquaria are usually limited by cost considerations. Adult frogs use their lungs when on land. Its main tank, which holds 7,500 cubic meters of water, features the world's largest acrylic panel measuring 8.2 meters by 22.5 meters with a thickness of 60 centimeters. When a frog is underwater, oxygen is transmitted through the skin directly into the bloodstream. The Okinawa Churaumi Aquarium is the world's second largest aquarium and part of the Ocean Expo Park located in Motobu, Okinawa. There are a number of blood vessels near the skin. At 56 feet long by 17 feet high (17 by 5 m), it used to be the largest window in the world and is over 13 inches (330 mm) thick. The skin of amphibians is moistened by secretions of mucus, and is used for respiration at times.

The Monterey Bay Aquarium has an acrylic viewing window into their largest tank. Just as frogs are able to absorb water through their skin, they are also able to breathe through their skin. gallons (1,500 m³). The egg and tadpole development is very fast in comparison to most frogs, to prevent the pond drying before metamorphosis. gallons (7,500 m³), as well as two others of 400,000 U.S. Once it rains, they will emerge, find a temporary pond and breed. The Shedd Aquarium features an individual aquarium of two million U.S. The Australia genus Cyclorana, and American genus Pternohyla will dig underground, form a water impervious cocoon and hibernate during dry periods.

Public aquaria designed for exhibition of large species or environments can be dramatically larger than any home aquarium. For this reason, for frogs to survive in deserts or drought prone regions, where water may not be accessible for many years, other adaptations must suffice. gallons (several cubic meters), at great effort and expense. These adaptations only reduce water loss enough for a predominately arboreal existence, and are not suitable for arid conditions. However, some dedicated aquarists have been known to construct custom aquaria of up to several thousand U.S. This position involves the frog lying with its toes and fingers tucked under its body and chin respectively, with no gap between the body and substrate. gallons). This includes nocturnal activity, and resting in a water conserving position.

gallon (1 kg/L)) and internal water pressure (requiring thick, strong glass siding) of a large aquarium, keep most home aquaria to a maximum of around 1 m³ (300 U.S. Some species will use behavioural traits to reduce water loss. Practical limitations, most notably the weight (water weighs about 8.3 pounds per U.S. Some tree frogs reduce water loss with a water proof layer of skin. This size is widely considered the smallest practical system with filtration and other basic systems; indeed, the local government of Rome has recently taken the step of banning traditional goldfish bowls as inhumane. Many frogs, such as tree frogs, have behaviourally and physiologically adapted to conserving water. gallons (11 L). However, the permeability of frog's skin also results in some frogs losing large amounts of water.

Aquaria kept in homes by hobbyists can be as small as 3 U.S. Many frogs are able to absorb water directly through their skin, especially through the pelvic area. In general, larger aquarium systems are typically recommended to hobbyists due to their resistance to rapid fluctuations of temperature and pH, allowing for greater system stability. The croak of the American bullfrog (Rana catesbiana) is sometimes spelt "jug o' rum". An aquarium can range from a small, unadorned glass bowl containing less than a liter of water – although generally unsuited for most fish (except, perhaps, air breathing fish such as Betta splendens or the Paradise Fish) – to massive tanks built in public aquaria which are limited only by engineering constraints and can house entire ecosystems as large as kelp forests or species of large sharks. This difference is due to the different species within each region (for example, Common frog (Rana temporaria) in Britain and Leopard frog (Rana pipiens) in the USA). Water temperature can be regulated with a combined thermometer/heater unit (or, more rarely, with a cooling unit), while water movement can be controlled through the use of powerheads and careful design of internal water flow (such as location of filtration system points of inflow and outflow). Frog noise tends to be spelt (for English speakers) as "crrrrk" in Britain and "ribbit" in the USA.

Aquarists may prefer anything from still water up to swift simulated currents in an aquarium, depending on the conditions best suited for the aquarium's inhabitants. Many species of frog have deep calls, or croaks. Water movement can also be important in accurately simulating a natural ecosystem. The effectiveness of the call is unknown, however it is suspected the call intrigues the predator, until another animal is attracted, distracting them enough for its escape. Cold water aquaria are those with temperatures below what would be considered tropical; a variety of fish are better suited to this cooler environment. This is done with the mouth open, and usually results in a higher pitched call. Most fish and plant species tolerate only a limited range of water temperatures: Tropical or warm water aquaria, with an average temperature of about 25 °C (78 °F), are much more common and house most popular aquarium fish. A distress call is emitted by some frogs when they are in a position of danger.

cold water. All of these calls are emitted with the mouth of the frog closed. The temperature of the water forms the basis of one of the two most basic aquarium classifications: tropical vs. Many species also have a territorial call that is used to chase away other males. Secondary water characteristics are also important to the success of an aquarium. A male frog will emit a different call when mounted by another male. In contrast, public aquaria with large water needs often locate themselves near a natural water source (such as a river, lake, or ocean) in order to have easy access to large volumes of water that does not require much further treatment. Polypedates leucomystax, produce a call reciprocal to the male's which acts as the catalyst for the enhancement of reproductive activity in the breeding colony (Roy, 1997).

More sophisticated aquarists may make other modifications to their base water source to modify the water's alkalinity, hardness, or dissolved content of organics and gases, before adding it to their aquaria. Females of many frog species, e.g. Brackish or saltwater aquaria require the addition of a mixture of salts and other minerals, which are commercially available for this purpose. Males will either call in a group, called a chorus, or individually. For freshwater aquaria, additives formulated to remove chlorine or chloramine (used to disinfect drinking water supplies for human consumption) are often all that is needed to make the water ready for aquarium use. The main reason for calling is for the male to attract a mate. Home aquarists typically use modified tap water supplied through their local municipal water system to fill their tanks. The flowing water overpowers any call, and they must communicate by other means.

Dissolved organic content and dissolved gases content are also important factors. Species of frog which have lost a vocal sack, and do not have a loud call, tend to inhabit areas close to flowing water. Hardness measures overall dissolved mineral content; soft or hard water may be preferred. Their buccal cavity is enlarged and dome shaped, acting as a resonance chamber, and amplifies their call. The pH of the water is a measure of alkalinity or acidity. Some frogs which lack vocal sacks, such as the frogs from the genera Heleioporus and Neobatrachus, can still have a loud call. Several other water characteristics result from dissolved contents of the water, and are important to the proper simulation of natural environments. Each call is unique to a species.

An aquarium may have fresh water (a salt level of < 0.5%), simulating a lake or river environment; salt water (a salt level of 5%–18%), simulating an ocean or sea environment; or brackish water (a salt level of 0.5%–5%), simulating environments lying between fresh and salt, such as estuaries. The vocal sac is a membrane of skin under the throat or on the corner of the mouth which distends during the amplification of the call. Salt content, or salinity, is the most basic classification of water conditions. In most calling frogs, the sound is amplified by the vocal sac(s). The dissolved content of water is perhaps the most important aspect of water conditions, as dissolved salts and other constituents can dramatically impact basic water chemistry, and therefore how organisms are able to interact with their environment. It will call by passing air through the larynx, in the throat. The size of an aquarium also limits the aquarist in what types of ecosystems he can reproduce, species selection, and biological loading. The males of most species of frogs will call for a variety of reasons.

The conditions and characteristics of the water contained in an aquarium are the most important classification criteria, as most aquatic life will not survive even limited exposure to unsuitable water conditions. The hind legs of ground dwelling frogs are better suited to hopping. Aquaria can be classified by several variables that determine the type of aquatic life that can be suitably housed. Ground dwelling frogs will usually have reduced toe pads (if any at all), and webbing. The combined function of these elements is to maintain appropriate water quality and characteristics suitable for the aquarium's residents. Ground dwelling frogs do not have much in the way of specific adaptations, except they lack the adaptations of aquatic and arboreal frogs. Size, lighting conditions, density of floating and rooted plants, placement of bogwood, creation of caves or overhangs, type of substrate, and other factors (including an aquarium's positioning within a room) can all affect the behavior and survivability of tank inhabitants. Therefore, many arboreal frogs have hips which allow both hopping and walking.

An aquarium's physical characteristics form another aspect of aquarium design. Transport through trees can be dangerous just through the process of hopping. Coolers are also available for use in cold water aquaria or in parts of the world where the ambient room temperature is above the desired tank temperature. This aids in creating the greatest surface area touching the substrate, by applying even pressure to the toes/fingers. Aquarium heaters are designed to act as thermostats to regulate water temperature at a level designated by the aquarist when the prevailing temperature of air surrounding the aquarium is below the desired water temperature. Tree frogs also have a small structure called the intercalory structure in their toes and fingers. These devices, once universal, are now somewhat less commonly used as some newer filtration systems create enough surface agitation to supply adequate gas exchange at the surface. [1].

Air pumps are employed to adequately oxygenate (or in the case of a heavily planted aquarium, provide carbon dioxide to) the water. For this reason, wet frogs cannot grip to smooth surfaces. Protein skimmers, filtration devices that remove proteins and other waste from the water, are usually found only in salt water aquaria. Capillarity then maintains the grip . Most systems use pumps to remove a small portion of the tank's water to an external pathway where filtration occurs; the filtered water is then returned to the aquarium. On smooth surfaces, the gaps drain away excess moisture, to produce a thin layer of moisture. Filtration systems are the most complexly engineered component of most home aquaria, and various designs are used. The pressure from the frog interlocks any irregularities on a surface, and therefore grips the surface.

Combined biological and mechanical filtration systems are now common; these are designed to remove potentially dangerous build up of nitrogenous wastes and phosphates dissolved in the water, as well as particulate matter. The cells on the pads are interlocking, with gaps between each cell. In addition, some freshwater tanks (and most saltwater tanks) use powerheads to increase water circulation. The toe discs do not work by suction, but a more complicated system. The common freshwater aquarium maintained by a home aquarist typically includes a filtration system, an artificial lighting system, air pumps, and a heater. Arboreal frogs have toe pads on the end of their toes to help grip. Freshwater aquaria remain the most popular due to their lower cost and easier maintenance, but marine (saltwater) aquaria have gained cachet as dedicated enthusiasts prove it is possible to preserve these challenging environments. For example, the African dwarf frog (Hymenochirus sp.) is completely aquatic and its hands are fully webbed, whereas White's tree frog is arboreal, and is only half or one quarter webbed.

The most successful aquaria, as judged by the long-term survivability of its inhabitants, carefully emulate the natural environments that their residents would occupy in the wild. The degree to which a frog is aquatic, can usually be predicted from the amount their hands/feet are webbed. Aquaria can vary in size from a small bowl large enough for a single small fish, to the huge public aquaria that can simulate entire marine ecosystems. To do this, frogs have evolved a structure similar to most semi-aquatic animals - webbed feet and hands. From the outdoor ponds and glass jars of antiquity, modern aquaria have evolved into a wide range of specialized systems. An aquatic lifestyle for a frog requires a frog to move fast through the water. In the United States, a large minority (40%) of aquarists maintain two or more tanks at any one time. The three main habitats are terrestrial, aquatic and arboreal.

The hobby has the strongest following in Europe, Asia, and North America. This is due to the large variety of habitats in which frogs inhabit. There are currently estimated to be about 60 million aquarium hobbyists worldwide, and many more aquaria kept by them. The feet/hands and legs of frogs, are one of the most varied structures within the order Anura. Popularization was also assisted by the availability of air freight, which allowed a much wider variety of fish to be successfully imported from distant regions of origin that consequently attracted new hobbyists. Hence, dead frogs are often used for dissections in high school and university anatomy classes, often after being injected with coloured plastics to enhance the contrast between different organs. With electricity great improvements were made in aquarium technology, allowing artificial lighting as well as the aeration, filtration, and heating of the water. The internal organs of frogs are relatively odourless.

Aquaria became more widely popular as houses became almost universally electrified after World War I. They have a tympanum on each side of their head, which is involved in hearing, and is covered by skin in some species. (One feature of some 19th-century aquaria that would prove curious to hobbyists today was the use of a metal base panel so that the aquarium water could be heated by flame.) Germans rivaled the British in their interest, and by the turn of the century Hamburg became the European port of entry for many newly seen species. Frogs have three eyelid membranes: one transparent to protect the eyes underwater, and two which are translucent to opaque. The framed-glass aquarium was a specialized version of the glazed Wardian case developed for British horticulturists in the 1830s to protect exotic plants on long sea voyages. The skin lacks keratin and hangs loosely on the body because of the lack of loose connective tissue, and can be smooth, warty or have skin folds. The keeping of fish in an aquarium first became a popular hobby in Britain only after ornate aquaria in cast-iron frames were featured at the Great Exhibition of 1851. Frogs range in size from 10mm (Psyllophryne didactyla of Brazil and Eleutherodactylus iberia of Cuba) to 300mm (Goliath frog, Conraua goliath, of Cameroon).

The concept of keeping aquatic life in glass containers, then, dates to at latest this period. They have a short vertebral column, with no more than ten free vertebrae, followed by a fused tail bone, usually resulting in a frog without a tail. In the 18th century, the biologist Abraham Trembley kept hydra found in the garden canals of the Bentinck residence 'Sorgvliet' in the Netherlands, in large cylindrical glass vessels for study. Frogs are generally well suited to jumping, and have long hind legs, with elongated ankle bones. In 1665 the diarist Samuel Pepys recorded seeing in London "a fine rarity, of fishes kept in a glass of water, that will live so forever, and finely marked they are, being foreign." The fish observed by Pepys were likely to have been the paradise fish, Macropodus opercularis, a familiar garden fish in Canton, China, where the East India Company was then trading. However, there are some general characteristics that distinguish them from other amphibians. However, it is difficult to pinpoint the exact date of this development. Because of the great diversity of frogs (approximately 5250 described species), many characteristics are not shared by all of the species.

The concept of an aquarium, designed for the observation of fish in an enclosed, transparent tank to be kept indoors, emerged more recently. . The Chinese brought goldfish indoors during the Song dynasty to enjoy them in large ceramic vessels. Their distribution ranges from tropic to subarctic regions, with most of the approximately 5250 described species found in tropical rainforest. Many other cultures also have a history of keeping fish for both functional and decorative purposes. Some frogs are poisonous and have warning colouration; others are well camouflaged. Depictions of the sacred fish of Oxyrhynchus kept in captivity in rectangular temple pools have been found in ancient Egyptian art. Most frogs have a semi-aquatic lifestyle, and their larvae, called tadpoles, have gills and develop in water.

In China, selective breeding of carp into today's popular koi and goldfish is believed to have begun over 2,000 years ago. "True frogs" are of the family Ranidae. Ancient Sumerians were known to keep wild-caught fish in ponds, before preparing them for meals. The only family exclusively given the common name "toad" is Bufonidae, but many species from various other families are also called "toads". The keeping of fish in confined or artificial environments is a practice with deep roots in history. A distinction based on appearance is often made between frogs and toads, but this has no scientific basis. The word aquarium itself is taken directly from the latin aqua, meaning water, with the suffix -rium, meaning "place" or "building". Adult frogs are characterised by long hindlegs, a short body, webbed digits, protruding eyes and the absence of a tail.

. Frog is the common name for amphibians in the order Anura. Other components in maintaining a suitable aquarium environment include appropriate species selection, management of biological loading, and good physical design. The nitrogen cycle describes the flow of nitrogen from input via food, through toxic nitrogenous waste produced by tank inhabitants, to metabolism to less toxic compounds by beneficial bacteria populations. Controlling water quality includes managing the inflow and outflow of nutrients, most notably the management of waste produced by tank inhabitants.

The careful aquarist dedicates considerable effort to maintaining a tank ecology that mimics its inhabitants' natural habitat. Inhabitants for aquaria are often collected from the wild, although there is a growing list of organisms that are bred in captivity for supply to the aquarium trade. These characteristics, and others, determine the type of fish and other inhabitants that can survive and thrive in the aquarium. Aquaria are usually classified as containing fresh or salt water, at tropical or cold water temperatures.

A wide variety of aquaria are now kept by hobbyists, ranging from a simple bowl housing a single fish to complex simulated ecosystems with carefully engineered support systems. gallons) and a collection of about 580 species of aquatic life. Public aquaria reproduce the home aquarist's hobby on a grand scale — the Osaka Aquarium, for example, boasts a tank of 5,400 m³ (1.4 million U.S. From the 1850s, when the predecessor of the modern aquarium was first developed as a novel curiosity, the ranks of aquarists have swelled as more sophisticated systems including lighting and filtration systems were developed to keep aquarium fish healthy.

Aquarium keeping is a popular hobby around the world, with about 60 million enthusiasts worldwide. An aquarium (plural aquariums or aquaria) is a vivarium, usually contained in a clear-sided container (typically constructed of glass or high-strength plastic) in which water-dwelling plants and animals (usually fish, and sometimes invertebrates, as well as amphibians, marine mammals, and reptiles) are kept in captivity, often for public display; or it is an establishment featuring such displays.

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