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95-463: Fish are vertebrates with gills and without digits. Fish or FISH may also refer to: Fish A fish ( pl. : fish or fishes ) is an aquatic , anamniotic , gill -bearing vertebrate animal with swimming fins and a hard skull , but lacking limbs with digits . Fish can be grouped into the more basal jawless fish and the more common jawed fish , the latter including all living cartilaginous and bony fish , as well as

190-1054: A dagger (†); groups of uncertain placement are labelled with a question mark (?) and dashed lines (- - - - -). Jawless fishes (118 species: hagfish , lampreys ) [REDACTED] † Thelodonti , † Conodonta , † Anaspida [REDACTED] [REDACTED] [REDACTED] † Galeaspida [REDACTED] † Osteostraci [REDACTED] † Placodermi [REDACTED] † Acanthodii [REDACTED]  (>1,100 species: sharks , rays , chimaeras ) [REDACTED]  (2 species: coelacanths ) [REDACTED] Dipnoi (6 species: lungfish ) [REDACTED] Tetrapoda (>38,000 species, not considered fish: amphibians, reptiles, birds, mammals) [REDACTED]  (14 species: bichirs , reedfish ) [REDACTED]  (27 species: sturgeons , paddlefish ) [REDACTED] Ginglymodi (7 species: gars , alligator gars ) [REDACTED] Halecomorphi (2 species: bowfin , eyetail bowfin ) [REDACTED]  (>32,000 species) [REDACTED] Fishes (without tetrapods) are

285-579: A paraphyletic group and for this reason, the class Pisces seen in older reference works is no longer used in formal classifications. Traditional classification divides fish into three extant classes (Agnatha, Chondrichthyes, and Osteichthyes), and with extinct forms sometimes classified within those groups, sometimes as their own classes. Fish account for more than half of vertebrate species. As of 2016, there are over 32,000 described species of bony fish, over 1,100 species of cartilaginous fish, and over 100 hagfish and lampreys. A third of these fall within

380-472: A saltwater aquarium , though he did not use the term. In 1846, Anne Thynne maintained stony corals and seaweed for almost three years, and was credited as the creator of the first balanced marine aquarium in London. English chemist Robert Warington experimented with a 13-gallon container, which contained goldfish, eelgrass , and snails , creating one of the first stable aquaria. The aquarium principle

475-414: A 400-litre (110 US gal; 88 imp gal) tank with many other fish in it represents only a minor change. For this reason, hobbyists often favor larger tanks, as they require less attention. Several nutrient cycles are important in the aquarium. Dissolved oxygen enters the system at the surface water-air interface. Similarly, carbon dioxide escapes the system into the air. The phosphate cycle

570-1166: A challenge to recreate such environments, and most "true" biotopes will only have a few (if not only one) species of fish and invertebrates. Finally, an emerging concept for the home is that of a wall mounted aquarium, some of which are displayed at the Living Art Marine Center . An aquarium can range from a small glass bowl containing less than 1 litre (2.1 US pt) of water to immense public aquaria that house entire ecosystems such as kelp forests . Relatively large home aquaria resist rapid fluctuations of temperature and pH , allowing for greater system stability. Beginner aquarists are advised to consider larger tanks to begin with, as controlling water parameters in smaller tanks can prove difficult. Small, unfiltered bowl-shaped aquaria are now widely regarded as unsuitable for most fish. In order to keep water conditions at suitable levels, aquariums should contain at least two forms of filtration : biological and mechanical. Chemical filtration should also be considered under some circumstances for optimum water quality. Chemical filtration

665-420: A circular, submerged lid. Pseudokreisels are "U" or semicircle shaped, usually without a lid. Stretch kreisels are a "double gyre" kreisel design, where the tank length is at least twice the height. Using two downwelling inlets on both sides of the tank lets gravity create two gyres in the tank. A single downwelling inlet may be used in the middle as well. The top of a stretch kreisel may be open or closed with

760-425: A cooler environment. Temperature consistency is more important than range. Most organisms are not accustomed to sudden changes in temperatures, which can cause shock and lead to disease. Water temperature can be regulated with a thermostat and heater (or cooler). Water movement can also be important in simulating a natural ecosystem. Aquarists may prefer anything from still water up to swift currents , depending on

855-444: A dazzling aquarium is one of the last surefire ways to impress their peers." A kreisel tank ( kreisel being German for " spinning top " or " gyroscope ") is an aquarium shaped like a horizontal cylinder that is designed to hold delicate animals such as jellyfish and newborn seahorses. These aquariums provide slow, circular water flow with a bare minimum of interior hardware to prevent the inhabitants from becoming injured by pumps or

950-399: A lid. There may also be screens about midway down the sides of the tank, or at the top on the sides. It is possible to combine these designs; a circular shaped tank is used without a lid or cover, and the surface of the water acts as the continuation of circular flow. Another popular setup is the biotope aquarium. A biotope aquarium is a recreation of a specific natural environment. Some of

1045-436: A more spherical lens . Their retinas generally have both rods and cones (for scotopic and photopic vision ); many species have colour vision , often with three types of cone. Teleosts can see polarized light ; some such as cyprinids have a fourth type of cone that detects ultraviolet . Amongst jawless fish , the lamprey has well-developed eyes, while the hagfish has only primitive eyespots. Hearing too

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1140-514: A natural water source (such as a river, lake, or ocean) to reduce the level of treatment. Some hobbyists use an algae scrubber to filter the water naturally. Water temperature determines the two most basic aquarium classifications: tropical versus cold water . Most fish and plant species tolerate only a limited temperature range; tropical aquaria, with an average temperature of about 25 °C (77 °F), are much more common. Temperate or coldwater aquaria are for fish that are better suited to

1235-433: A popular choice for many home and hobbyist aquarists for many years. Once silicone sealant became strong enough to ensure a long-term water-tight seal, it eliminated the need for a structural frame. In addition to lower cost, glass aquaria are more scratch resistant than acrylic. Although the price is one of the main considerations for aquarists when deciding which of these two types of aquaria to purchase, for very large tanks,

1330-419: A protective bony cover or operculum . They are able to oxygenate their gills using muscles in the head. Some 400 species of fish in 50 families can breathe air, enabling them to live in oxygen-poor water or to emerge on to land. The ability of fish to do this is potentially limited by their single-loop circulation, as oxygenated blood from their air-breathing organ will mix with deoxygenated blood returning to

1425-403: A quantum radical pair mechanism . Aquarium The aquarium principle was fully developed in 1850 by the chemist Robert Warington , who explained that plants added to water in a container would give off enough oxygen to support animals, so long as the numbers of animals did not grow too large. The aquarium craze was launched in early Victorian England by Gosse, who created and stocked

1520-441: A sense of touch and of hearing . Blind cave fish navigate almost entirely through the sensations from their lateral line system. Some fish, such as catfish and sharks, have the ampullae of Lorenzini , electroreceptors that detect weak electric currents on the order of millivolt. Vision is an important sensory system in fish. Fish eyes are similar to those of terrestrial vertebrates like birds and mammals, but have

1615-465: A small glass bowl, a few liters in volume, to immense public aquaria of thousands of liters. Specialized equipment maintains appropriate water quality and other characteristics suitable for the aquarium's residents. In 1369, the Hongwu Emperor of China established a porcelain company that produced large porcelain tubs for maintaining goldfish ; over time, people produced tubs that approached

1710-485: A tail fin, jaws, skin covered with scales , and lays eggs. Each criterion has exceptions, creating a wide diversity in body shape and way of life. For example, some fast-swimming fish are warm-blooded, while some slow-swimming fish have abandoned streamlining in favour of other body shapes. Fish species are roughly divided equally between freshwater and marine (oceanic) ecosystems; there are some 15,200 freshwater species and around 14,800 marine species. Coral reefs in

1805-401: A tank by diluting effects from death or contamination events that push an aquarium away from equilibrium. The bigger the tank, the easier such a systemic shock is to absorb, because the effects of that event are diluted. For example, the death of the only fish in an 11-litre (3 US gal; 2 imp gal) tank causes dramatic changes in the system, while the death of that same fish in

1900-449: A tropical temperature and requires less capacity from an aquarium heater. Acrylic-soluble cements are used to directly fuse acrylic together. Acrylic allows for the formation of unusual shapes, such as the hexagonal tank. Acrylics are easier to scratch than glass, but unlike glass, scratches in acrylic can be polished out. Large aquaria might instead use stronger materials such as fiberglass -reinforced plastics . However, this material

1995-589: A true "land fish" as this worm-like catfish strictly lives among waterlogged leaf litter . Cavefish of multiple families live in underground lakes , underground rivers or aquifers . Like other animals, fish suffer from parasitism . Some species use cleaner fish to remove external parasites. The best known of these are the bluestreak cleaner wrasses of coral reefs in the Indian and Pacific oceans. These small fish maintain cleaning stations where other fish congregate and perform specific movements to attract

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2090-422: A typical fish is adapted for efficient swimming by alternately contracting paired sets of muscles on either side of the backbone. These contractions form S-shaped curves that move down the body. As each curve reaches the tail fin, force is applied to the water, moving the fish forward. The other fins act as control surfaces like an aircraft's flaps, enabling the fish to steer in any direction. Since body tissue

2185-465: Is an important sensory system in fish. Fish sense sound using their lateral lines and otoliths in their ears, inside their heads. Some can detect sound through the swim bladder. Some fish, including salmon, are capable of magnetoreception ; when the axis of a magnetic field is changed around a circular tank of young fish, they reorient themselves in line with the field. The mechanism of fish magnetoreception remains unknown; experiments in birds imply

2280-431: 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 enough to keep these other nutrient cycles in approximate equilibrium. An aquarium must be maintained regularly to ensure that

2375-431: Is denser than water, fish must compensate for the difference or they will sink. Many bony fish have an internal organ called a swim bladder that allows them to adjust their buoyancy by increasing or decreasing the amount of gas it contains. The scales of fish provide protection from predators at the cost of adding stiffness and weight. Fish scales are often highly reflective; this silvering provides camouflage in

2470-436: Is frequently achieved via activated carbon , to filter medications, tannins , and/or other known impurities from the water. Reef aquaria under 100 litres (26 US gal; 22 imp gal) have a special place in the aquarium hobby; these aquaria, termed nano reefs (when used in reefkeeping), have a small water volume, under 40 litres (11 US gal; 9 imp gal). Practical limitations, most notably

2565-614: Is keeping them in a wall. Here the use of plywood is hidden by sinking the aquarium inside the wall. Putting insulation between the two helps with the insulation of a heated tank. Objects used for aquariums include: coffee tables, sinks, and even toilets. Another such example is the MacQuarium , an aquarium made from the shell of an Apple Macintosh computer . In recent years, elaborate custom-designed home aquariums costing hundreds of thousands of dollars have become status symbols—according to The New York Times , "among people of means,

2660-471: Is not transparent. Reinforced concrete is used for aquaria where weight and space are not factors. Concrete must be coated with a waterproof layer to prevent the water from breaking down the concrete, as well as preventing contamination of the water by the concrete. Plywood can also be used when building aquaria. The benefits of using plywood include: lower construction costs, less weight, and better insulation. A popular positioning choice for plywood aquaria

2755-478: Is only a portion of the complete 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 become bound in the biomass of plants. The aquarium keeper must remove water once nitrate concentrations grow, or remove plants which have grown from the nitrates. Hobbyist aquaria often do not have sufficient bacteria populations to adequately denitrify waste. This problem

2850-465: Is the biggest part of the brain; it is small in hagfish and lampreys , but very large in mormyrids , processing their electrical sense . The brain stem or myelencephalon controls some muscles and body organs, and governs respiration and osmoregulation . The lateral line system is a network of sensors in the skin which detects gentle currents and vibrations, and senses the motion of nearby fish, whether predators or prey. This can be considered both

2945-518: Is the most basic measure of water conditions. An aquarium may have freshwater (salinity below 500 parts per million), simulating a lake or river environment; brackish water (a salt level of 500 to 30,000 PPM), simulating environments lying between fresh and salt, such as estuaries ; and salt water or seawater (a salt level of 30,000 to 40,000 PPM), simulating an ocean environment. Rarely, higher salt concentrations are maintained in specialized tanks for raising brine organisms. Saltwater

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3040-415: Is to have very small aquariums, termed mini aquariums (less than 150 litres or 40 gallons) or nano aquariums (less than 75 litres or 20 gallons). These can be either freshwater or saltwater, and are intended to display a tiny but self-contained ecosystem. The typical hobbyist aquarium includes a filtration system, an artificial lighting system, an air diffuser and pump, and a heater or chiller depending on

3135-499: Is toxic to fish in high concentrations. Another type of bacteria (genus Nitrospira ) converts nitrite into nitrate , a less toxic substance. ( Nitrobacter bacteria were previously believed to fill this role. 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.) However, commercial products sold as kits to "jump start"

3230-541: Is usually alkaline, while the pH ( alkalinity or acidity ) of fresh water varies more. Hardness measures overall dissolved mineral content; hard or soft water may be preferred. Hard water is usually alkaline, while soft water is usually neutral to acidic. Dissolved organic content and dissolved gases content are also important factors. Home aquarists typically use tap water supplied through their local water supply network to fill their tanks. Straight tap water cannot be used in localities that pipe chlorinated water. In

3325-617: The Gnathostomata or (for bony fish) Osteichthyes , also contains the clade of tetrapods (four-limbed vertebrates, mostly terrestrial), which are usually not considered fish. Some tetrapods, such as cetaceans and ichthyosaurs , have secondarily acquired a fish-like body shape through convergent evolution . Fishes of the World comments that "it is increasingly widely accepted that tetrapods, including ourselves, are simply modified bony fishes, and so we are comfortable with using

3420-826: The Great Exhibition of 1851. In 1853, the aquarium craze was launched in England by Philip Henry Gosse who created and stocked the first public aquarium in the London Zoo which came to be known as the Fish House. Gosse coined the word "aquarium", opting for this term (instead of "aquatic vivarium" or "aqua-vivarium") in 1854 in his book The Aquariums: An Unveiling of the Wonders of the Deep Water . In this book, Gosse primarily discussed saltwater aquaria. In

3515-723: The Indo-Pacific constitute the center of diversity for marine fishes, whereas continental freshwater fishes are most diverse in large river basins of tropical rainforests , especially the Amazon , Congo , and Mekong basins. More than 5,600 fish species inhabit Neotropical freshwaters alone, such that Neotropical fishes represent about 10% of all vertebrate species on the Earth. Fish are abundant in most bodies of water. They can be found in nearly all aquatic environments, from high mountain streams (e.g., char and gudgeon ) to

3610-572: The Paleozoic , diversifying into many forms. The earliest fish with dedicated respiratory gills and paired fins , the ostracoderms , had heavy bony plates that served as protective exoskeletons against invertebrate predators . The first fish with jaws , the placoderms, appeared in the Silurian and greatly diversified during the Devonian , the "Age of Fishes". Bony fish, distinguished by

3705-571: The Silurian , with giant armoured placoderms such as Dunkleosteus . Jawed fish, too, appeared during the Silurian: the cartilaginous Chondrichthyes and the bony Osteichthyes . During the Devonian , fish diversity greatly increased, including among the placoderms, lobe-finned fishes, and early sharks, earning the Devonian the epithet "the age of fishes". Fishes are a paraphyletic group, since any clade containing all fish, such as

3800-554: The Victorian era in the United Kingdom, a common design for the home aquarium was a glass front with the other sides made of wood (made watertight with a pitch coating). The bottom would be made of slate and heated from below. More advanced systems soon began to be introduced, along with tanks of glass in metal frames. During the latter half of the 19th century, a variety of aquarium designs were explored, such as hanging

3895-477: The abyssal and even hadal depths of the deepest oceans (e.g., cusk-eels and snailfish ), although none have been found in the deepest 25% of the ocean. The deepest living fish in the ocean so far found is a cusk-eel, Abyssobrotula galatheae , recorded at the bottom of the Puerto Rico Trench at 8,370 m (27,460 ft). In terms of temperature, Jonah's icefish live in cold waters of

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3990-611: The aquascaping designs of Takashi Amano influencing fishkeepers to treat home aquariums as aesthetically pleasing compositions, rather than simply as a way of displaying fish specimens. In the United States, as of 1996, aquarium keeping is the second-most popular hobby after stamp collecting . In 1999, an estimated 9.6 million US households owned an aquarium. Figures from the 2005/2006 APPMA National Pet Owners Survey report that Americans own approximately 139 million freshwater fish and 9.6 million saltwater fish. Estimates of

4085-447: The gravel , or other substrate if the aquarium has one; however some manage to avoid this entirely by keeping it somewhat self-sufficient. A good habit is to remove the water being replaced by "vacuuming" the gravel with suitable implements, as this will eliminate uneaten foods and other residues that settle on the substrate . In many areas tap water is not considered to be safe for fish to live in because it contains chemicals that harm

4180-400: The intertidal zone , are facultative air breathers, able to breathe air when out of water, as may occur daily at low tide , and to use their gills when in water. Some coastal fish like rockskippers and mudskippers choose to leave the water to feed in habitats temporarily exposed to the air. Some catfish absorb air through their digestive tracts. The digestive system consists of a tube,

4275-481: The nitrogen cycle or be removed by passing through zeolite . 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. In the wild, the vast amount of water surrounding the fish dilutes ammonia and other waste materials. When fish are put into an aquarium, waste can quickly reach toxic concentrations in

4370-425: The stout infantfish . Swimming performance varies from fish such as tuna, salmon , and jacks that can cover 10–20 body-lengths per second to species such as eels and rays that swim no more than 0.5 body-lengths per second. A typical fish is cold-blooded , has a streamlined body for rapid swimming, extracts oxygen from water using gills, has two sets of paired fins, one or two dorsal fins, an anal fin and

4465-661: The weight of water (1 kilogram per litre (8.345 lb/U.S. gal; 10.022 lb/imp gal)) and internal water pressure (requiring thick glass siding) of a large aquarium, restrict most home aquaria to a maximum of around 1 cubic metre in volume (1000 L, weighing 1,000 kg or 2,200 lb ). Some aquarists, however, have constructed aquaria of many thousands of litres. Public aquariums and oceanariums designed for exhibition of large species or environments can be dramatically larger than any home aquarium. The Georgia Aquarium , for example, features an individual aquarium of 6,300,000 US gallons (24,000,000 L). A new trend

4560-429: The 1850s, the aquarium became a fad in the United Kingdom. Tank designs and techniques for maintaining water quality were developed by Warington, later cooperating with Gosse until his critical review of the tank water composition. Edward Edwards developed these glass-fronted aquaria in his 1858 patent for a "dark-water-chamber slope-back tank", with water slowly circulating to a reservoir beneath. Germans soon rivaled

4655-520: The 1960s, metal frames made marine aquaria almost impossible due to corrosion, but the development of tar and silicone sealant allowed the first all-glass aquaria made by Martin Horowitz in Los Angeles, CA. The frames remained, however, though purely for aesthetic reasons. Japan played an increasingly important role in shaping aquarium design in the latter part of the twentieth century, with

4750-649: The British in their interest. In 1854, an anonymous author had two articles published about the saltwater aquaria of the United Kingdom: Die Gartenlaube (The Garden House) entitled Der Ocean auf dem Tische (The Ocean on the Table). However, in 1856, Der See im Glase (The Lake in a Glass) was published, discussing freshwater aquaria, which were much easier to maintain in landlocked areas. In 1862 William Alford Lloyd , then bankrupt because of

4845-601: The Southern Ocean, including under the Filchner–Ronne Ice Shelf at a latitude of 79°S, while desert pupfish live in desert springs, streams, and marshes, sometimes highly saline, with water temperatures as high as 36 C. A few fish live mostly on land or lay their eggs on land near water. Mudskippers feed and interact with one another on mudflats and go underwater to hide in their burrows. A single undescribed species of Phreatobius has been called

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4940-482: The addition of a commercially available mixture of salts and other minerals. Some aquarists modify water's alkalinity, hardness, or dissolved content of organics and gases, before adding it to their aquaria. This can be accomplished by additives, such as sodium bicarbonate, to raise pH. Some aquarists filter or purify their water through deionization or reverse osmosis prior to using it. In contrast, public aquaria with large water needs often locate themselves near

5035-548: The aquarium on a wall, mounting it as part of a window , or even combining it with a birdcage . Around 1908, the first mechanical aquarium air pump was invented, powered by running water, instead of electricity. The introduction of the air pump into the hobby is considered by several historians of the hobby to be a pivotal moment in its development. Aquaria became more widely popular as houses had an electricity supply after World War I . Electricity allowed artificial lighting, as well as aeration , filtration , and heating of

5130-505: The aquarium's inhabitants. Many aquaria incorporate a hood, containing the lights, to decrease evaporation and prevent fish from leaving the aquarium (and anything else from entering the aquarium). Combined biological and mechanical aquarium filtration systems are common. These either convert ammonia to nitrate (removing nitrogen at the expense of aquatic plants), or to sometimes remove phosphate . Filter media can house microbes that mediate nitrification . Filtration systems are sometimes

5225-491: The aquarium's inhabitants. Water movement can be controlled via aeration from air pumps, powerheads, and careful design of internal water flow (such as location of filtration system points of inflow and outflow). Of primary concern to the aquarist is management of the waste produced by an aquarium's inhabitants. Fish, invertebrates, fungi , and some bacteria excrete nitrogen waste in the form of ammonia (which converts to ammonium , in water) and must then either pass through

5320-602: The aquarium. According to the July issue of The North American Review of the same year, William Stimson may have owned some of the first functional aquaria, and had as many as seven or eight. The first aquarist society in the United States was founded in New York City in 1893, followed by others. The New York Aquarium Journal , first published in October 1876, is considered to be the world's first aquarium magazine. In

5415-556: The attention of the cleaners. Cleaning behaviors have been observed in a number of fish groups, including an interesting case between two cichlids of the same genus, Etroplus maculatus , the cleaner, and the much larger E. suratensis . Fish occupy many trophic levels in freshwater and marine food webs . Fish at the higher levels are predatory , and a substantial part of their prey consists of other fish. In addition, mammals such as dolphins and seals feed on fish, alongside birds such as gannets and cormorants . The body of

5510-460: The behavior and survival of tank inhabitants. An aquarium can be placed on an aquarium stand. Because of the weight of the aquarium, a stand must be strong as well as level. A tank that is not level may distort, leak, or crack. These are often built with cabinets to allow storage, available in many styles to match room decor . Simple metal tank stands are also available. Most aquaria should be placed on polystyrene to cushion any irregularities on

5605-550: The body, and produce a concentrated urine. The reverse happens in freshwater fish : they tend to gain water osmotically, and produce a dilute urine. Some fish have kidneys able to operate in both freshwater and saltwater. Fish have small brains relative to body size compared with other vertebrates, typically one-fifteenth the brain mass of a similarly sized bird or mammal. However, some fish have relatively large brains, notably mormyrids and sharks , which have brains about as large for their body weight as birds and marsupials . At

5700-529: The craze in England being over, moved to Grindel Dammthor, Hamburg, to supervise the installation of the circulating system and tanks at the Hamburg Aquarium . During the 1870s, some of the first aquarist societies were appearing in Germany. The United States soon followed. Published in 1858, Henry D. Butler's The Family Aquarium was one of the first books written in the United States solely about

5795-421: The enclosed environment unless the tank is cycled to remove waste. A well-balanced tank contains organisms that are able to metabolize the waste products of other aquarium residents, recreating a portion of the nitrogen cycle . Bacteria known as nitrifiers (genus Nitrosomonas ) metabolize nitrogen waste. Nitrifying bacteria capture ammonia from the water and metabolize it to produce nitrite . Nitrite

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5890-570: The exact root is unknown; some authorities reconstruct a Proto-Indo-European root * peysk- , attested only in Italic , Celtic , and Germanic . About 530 million years ago during the Cambrian explosion , fishlike animals with a notochord and eyes at the front of the body, such as Haikouichthys , appear in the fossil record . During the late Cambrian , other jawless forms such as conodonts appear. Jawed vertebrates appear in

5985-445: The extinct placoderms and acanthodians . Most fish are cold-blooded , their body temperature varying with the surrounding water, though some large active swimmers like white shark and tuna can hold a higher core temperature . Many fish can communicate acoustically with each other, such as during courtship displays . The earliest fish appeared during the Cambrian as small filter feeders ; they continued to evolve through

6080-779: The first public aquarium at the London Zoo in 1853, and published the first manual, The Aquarium: An Unveiling of the Wonders of the Deep Sea in 1854. Small aquariums are kept in the home by hobbyists . There are large public aquariums in many cities. Public aquariums keep fish and other aquatic animals in large tanks. A large aquarium may have otters , dolphins , sharks , penguins , seals , and whales . Many aquarium tanks also have plants. An aquarist owns fish or maintains an aquarium, typically constructed of glass or high-strength acrylic . Aquaria with flat walls are known as fish tanks or simply tanks, while those with rounded walls are known as fish bowls . Size can range from

6175-557: The first person to create aquaria for experimenting with aquatic organisms. This experimentation lead to several discoveries, including the first direct evidence that argonauts , a marine cephalopod, create their own shells. In 1836, soon after his invention of the Wardian case , Dr. Nathaniel Bagshaw Ward proposed to use his tanks for tropical animals. In 1841 he did so, though only with aquatic plants and toy fish. However, he soon housed real animals. In 1838, Félix Dujardin noted owning

6270-416: The fish are kept healthy. Daily maintenance consists of checking the fish for signs of stress and disease . Also, aquarists must make sure that the water has a good quality and it is not cloudy or foamy and the temperature of the water is appropriate for the particular species of fish that live in the aquarium. Typical weekly maintenance includes changing around 10–30% or more of the water while cleaning

6365-594: The fish. Tap water from those areas must be treated with a suitable water conditioner, such as a product which removes chlorine and chloramine and neutralizes any heavy metals present. The water conditions must be checked both in the tank and in the replacement water, to make sure they are suitable for the species. The solute content of water is perhaps the most important aspect of water conditions, as total dissolved solids and other constituents dramatically impact basic water chemistry, and therefore how organisms interact with their environment. Salt content, or salinity ,

6460-405: The front of the brain are the olfactory lobes , a pair of structures that receive and process signals from the nostrils via the two olfactory nerves . Fish that hunt primarily by smell, such as hagfish and sharks, have very large olfactory lobes. Behind these is the telencephalon , which in fish deals mostly with olfaction. Together these structures form the forebrain. Connecting the forebrain to

6555-412: The gills flows in the opposite direction to the water, resulting in efficient countercurrent exchange . The gills push the oxygen-poor water out through openings in the sides of the pharynx. Cartilaginous fish have multiple gill openings: sharks usually have five, sometimes six or seven pairs; they often have to swim to oxygenate their gills. Bony fish have a single gill opening on each side, hidden beneath

6650-532: The gills. Oxygen-rich blood then flows without further pumping, unlike in mammals, to the body tissues. Finally, oxygen-depleted blood returns to the heart. Fish exchange gases using gills on either side of the pharynx . Gills consist of comblike structures called filaments. Each filament contains a capillary network that provides a large surface area for exchanging oxygen and carbon dioxide . Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills. Capillary blood in

6745-473: The glass panels attached with metal frames and sealed with putty. Metal-framed aquariums were still available until the mid-1960s, when the modern, silicone-sealed style replaced them. Acrylic aquariums first became available to the public in the 1970s. Laminated glass is sometimes used, which combines the advantages of both glass and acrylic. Today, most aquaria consist of glass panes bonded together by 100% silicone sealant, with plastic frames attached to

6840-447: The gut, leading from the mouth to the anus. The mouth of most fishes contains teeth to grip prey, bite off or scrape plant material, or crush the food. An esophagus carries food to the stomach where it may be stored and partially digested. A sphincter, the pylorus, releases food to the intestine at intervals. Many fish have finger-shaped pouches, pyloric caeca , around the pylorus, of doubtful function. The pancreas secretes enzymes into

6935-457: The heart from the rest of the body. Lungfish, bichirs, ropefish, bowfins, snakefish, and the African knifefish have evolved to reduce such mixing, and to reduce oxygen loss from the gills to oxygen-poor water. Bichirs and lungfish have tetrapod-like paired lungs, requiring them to surface to gulp air, and making them obligate air breathers. Many other fish, including inhabitants of rock pools and

7030-455: The intestine to digest the food; other enzymes are secreted directly by the intestine itself. The liver produces bile which helps to break up fat into an emulsion which can be absorbed in the intestine. Most fish release their nitrogenous wastes as ammonia . This may be excreted through the gills or filtered by the kidneys . Salt is excreted by the rectal gland. Saltwater fish tend to lose water by osmosis ; their kidneys return water to

7125-419: The midbrain is the diencephalon ; it works with hormones and homeostasis . The pineal body is just above the diencephalon; it detects light, maintains circadian rhythms, and controls color changes. The midbrain contains the two optic lobes . These are very large in species that hunt by sight, such as rainbow trout and cichlids . The hindbrain controls swimming and balance.The single-lobed cerebellum

7220-678: The most complex component of home aquaria. Aquarium heaters combine a heating element with a thermostat , allowing the aquarist to regulate water temperature at a level above that of the surrounding air, whereas coolers and chillers (refrigeration devices) are for use anywhere, such as cold water aquaria, where the ambient room temperature is above the desired tank temperature. Thermometers used include glass alcohol thermometers, adhesive external plastic strip thermometers , and battery-powered LCD thermometers. In addition, some aquarists use air pumps attached to airstones or water pumps to increase water circulation and supply adequate gas exchange at

7315-661: The most popular biotopes are the freshwater habitats of the Amazon River , the Rio Negro River, the African rift lake environments of Lake Malawi and Lake Tanganyika , and saltwater coral reefs of Australia , the Red Sea , and the Caribbean Sea . The fish, plants, substrate, rocks, wood, coral, and any other component of the display should completely match that of the local natural environment. It can be

7410-443: The nine largest families; from largest to smallest, these are Cyprinidae , Gobiidae , Cichlidae , Characidae , Loricariidae , Balitoridae , Serranidae , Labridae , and Scorpaenidae . About 64 families are monotypic , containing only one species. Fish range in size from the huge 16-metre (52 ft) whale shark to some tiny teleosts only 8-millimetre (0.3 in) long, such as the cyprinid Paedocypris progenetica and

7505-539: The nitrogen cycle often still contain Nitrobacter . 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 that decays more slowly than ammonia-driven plankton already dissolved in the water. Some hobbyists also use "anoxic filtration," which relies on bacteria that live in low-oxygen environments. The nitrogen cycle in an aquarium

7600-484: The numbers of fish kept in aquaria in Germany suggest at least 36 million. The hobby has the strongest following in Europe, Asia, and North America. In the United States, 40% of aquarists maintain two or more tanks. Over time, there has been an increasing appreciation of the usefulness of access to an aquarium to provide potential stress reduction and improvement of mood in people observing aquatic life. According to

7695-500: The ocean. Fish are caught for recreation , or raised by fishkeepers as ornaments for private and public exhibition in aquaria and garden ponds . Fish have had a role in human culture through the ages, serving as deities , religious symbols, and as the subjects of art, books and movies. The word fish is inherited from Proto-Germanic , and is related to German Fisch , the Latin piscis and Old Irish īasc , though

7790-402: The open ocean. Because the water all around is the same colour, reflecting an image of the water offers near-invisibility. Fish have a closed-loop circulatory system . The heart pumps the blood in a single loop throughout the body; for comparison, the mammal heart has two loops, one for the lungs to pick up oxygen, one for the body to deliver the oxygen. In fish, the heart pumps blood through

7885-410: The past, it was possible to "condition" the water by simply letting the water stand for a day or two, which allows the chlorine time to dissipate. However, chloramine is now used more often and does not leave the water as readily. Water conditioners formulated to remove chlorine or chloramine are often all that is needed to make the water ready for aquarium use. Brackish or saltwater aquaria require

7980-463: The presence of swim bladders and later ossified endoskeletons , emerged as the dominant group of fish after the end-Devonian extinction wiped out the apex placoderms. Bony fish are further divided into the lobe-finned and ray-finned fish . About 96% of all living fish species today are teleosts , a crown group of ray-finned fish that can protrude their jaws . The tetrapods , a mostly terrestrial clade of vertebrates that have dominated

8075-428: The price difference tends to disappear. Acrylic aquaria are now the primary competitor with glass. Prior to the invention of UV stabilization , early acrylic aquaria discolored over time with exposure to light; this is no longer the case. Acrylic is generally stronger than glass, weighs less, and provides a certain amount of temperature insulation. In colder climates or environments, it is easier to achieve and maintain

8170-532: The research of having an aquarium is many health benefits like reduce stress, blood pressure and heart rate improvement, better quality sleep , reduce anxiety and pain , therapy of excited children, Alzheimer's therapy and improve productivity . The first modern aquarium made of glass was developed in the 19th century by Robert Warrington. During the Victorian age , glass aquariums commonly had slate or steel bottoms, which allowed them to be heated underneath by an open-flame heat source. These aquariums had

8265-486: The shape of modern fish bowls. Leonhard Baldner , who wrote Vogel-, Fisch- und Tierbuch (Bird, Fish, and Animal Book) in 1666, maintained weather loaches and newts . It is sometimes held that the aquarium was invented by the Romans, who are said to have kept sea barbels in marble-and-glass tanks, but scholars doubt the veracity of this. In 1832, Jeanne Villepreux-Power , a pioneering French marine biologist, became

8360-399: The tank itself. The tank has no sharp angles around its sides and keeps the housed animals away from plumbing. Water moving into the tank gives a gentle flow that keeps the inhabitants suspended. Water leaves the tank through a screen which prevents animals from being drawn into the pump intake or overflow line. There are several types of kreisel tanks. In a true kreisel, a circular tank has

8455-415: The taxon Osteichthyes as a clade, which now includes all tetrapods". The biodiversity of extant fish is unevenly distributed among the various groups; teleosts , bony fishes able to protrude their jaws , make up 96% of fish species. The cladogram shows the evolutionary relationships of all groups of living fishes (with their respective diversity ) and the tetrapods. Extinct groups are marked with

8550-702: The top trophic levels in both aquatic and terrestrial ecosystems since the Late Paleozoic , evolved from lobe-finned fish during the Carboniferous , developing air-breathing lungs homologous to swim bladders. Despite the cladistic lineage, tetrapods are usually not considered to be fish, making "fish" a paraphyletic group. Fish have been an important natural resource for humans since prehistoric times, especially as food . Commercial and subsistence fishers harvest fish in wild fisheries or farm them in ponds or in breeding cages in

8645-579: The underlying surface or the bottom of the tank itself that may cause cracks. However, some tanks have an underframe making this unnecessary. Another important consideration for aquariums is their electrical usage. Water is expensive to keep heated, along with the lights that many aquariums, especially those with live plants have. New aquarists should also pay close attention to their electrical setup for their aquarium, taking care to set up power connections with drip loops to prevent water from getting to outlets. Large volumes of water enable more stability in

8740-580: The upper and lower edges for decoration. The glass aquarium is standard for sizes up to about 1,000 litres (260 US gal; 220 imp gal). However, glass is brittle and has very little give before fracturing, though generally the sealant fails first. Aquaria are made in a variety of shapes, such as cuboid , hexagonal , angled to fit in a corner (L-shaped), and bow-front (the front side curves outwards). Fish bowls are generally either made of plastic or glass, and are either spherical or some other round configuration in shape. Glass aquaria have been

8835-400: The water surface. Wave-making devices have also been constructed to provide wave action. An aquarium's physical characteristics form another aspect of aquarium design. Size, lighting conditions, density of floating and rooted plants, placement of bog-wood , creation of caves or overhangs, type of substrate , and other factors (including an aquarium's positioning within a room) can all affect

8930-611: The water. Initially, amateur aquarists kept native fish (with the exception of goldfish); the availability of exotic species from overseas further increased the popularity of the aquarium. Jugs made from a variety of materials were used to import fish from overseas, with a bicycle foot pump for aeration. Plastic shipping bags were introduced in the 1950s, making it easier to ship fish. The eventual availability of air freight allowed fish to be successfully imported from distant regions. Popular publications started by Herbert R. Axelrod influenced many more hobbyists to start keeping fish. In

9025-505: Was fully developed by Warington, explaining that plants added to water in a container would give off enough oxygen to support animals, so long as their numbers do not grow too large. He published his findings in 1850 in the Chemical Society's journal . The keeping of fish in an aquarium became a popular hobby and spread quickly. In the United Kingdom, it became popular after ornate aquaria in cast-iron frames were featured at

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