Tropical fish are

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

found in aquatic

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

environments around the world. Fishkeepers often keep tropical fish in

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

and saltwater

aquarium An aquarium (: aquariums or aquaria) is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. fishkeeping, Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aquati ...

s. The term "tropical fish" is not a taxonomic group, but rather is a general term for fish found in such environments, particularly those kept in aquariums.

Aquarium fish

Tropical fish is a term commonly used to refer to fish that are kept in heated aquariums. Freshwater tropical fish are more commonly kept than saltwater tropical fish due to the common availability of fresh water sources, such as tap water, whereas salt water is not commonly available and has to be recreated by using fresh water with sea salt additions. Salt water has to be monitored to maintain the correct salinity because of the effects of evaporation. Freshwater tropical aquariums can be maintained by simply topping up with fresh water. Tropical fish are popular choices for aquariums due to their often bright coloration, which typically derives from both

pigment A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

ed cells and

iridescent Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear gradually to change colour as the angle of view or the angle of illumination changes. Iridescence is caused by wave interference of light in microstruc ...

cells. Tropical fish may include wild-caught specimens, individuals born in captivity including lines selectively bred for special physical features, such as long fins, or particular colorations, such as

albino Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and reddish pink or blue eyes. Individuals with the condition are referred to as albinos. Varied use and interpretation of ...

. Some fish may be hybrids of more than one species.

Freshwater tropical fish

Most fish that are sold as tropical fish are freshwater species. Most species available are generally bred from fish farms in the far east and Florida where tropical temperatures make the commercial production more viable.

Mass production Mass production, also known as mass production, series production, series manufacture, or continuous production, is the production of substantial amounts of standardized products in a constant flow, including and especially on assembly lines ...

of tropical fish from farms has led to many inexpensive fish available to aquarists. Tropical freshwater fish are the most popular group of fish because of the low price and ease of keeping in aquaria. Some species are difficult to breed in captivity and so are still sourced from the wild. These species are generally more expensive. Among the bred-in-captivity species, the most expensive freshwater species include arowanas and flowerhorn cichlids. Some male flowerhorns are sterile due to many cross breedings.

Saltwater tropical fish

Marine fish that are sold as tropical fish are generally sourced from the wild, usually from the coral reefs around the world. This is because only a few species of marine fish have been successfully bred in captivity with any regularity. The price of marine fish coupled with the difficulty in keeping them alive in aquaria makes them less of a popular choice for aquarists to keep. However, because of the more vivid colours, patterns and behaviour of marine fish compared to freshwater fish, they are still reasonably popular. The advances in filtration technology and increase in available knowledge on how to maintain marine fish as well as the increasing number of aquarium-bred species is seeing a gradual rise in their popularity.

Coral reef tropical fish

Many marine tropical fish, particularly those of interest to fishkeepers, are those that live among or in close relation to

coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in group ...

s. Coral reefs form complex

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

s with tremendous

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

. Among ocean inhabitants, tropical fish stand out as particularly colorful. Hundreds of species can exist in a small area of a healthy reef, many of them hidden or well

camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...

d. Reef fish have developed many ingenious specialisations adapted to survival on the reefs. Some recreational scuba divers keep lists of fish species they have observed while diving, especially in tropical marine environments. Coral reefs occupy less than 1% of the surface area of the world oceans,Corals and Coral Reefs - Smithsonian Institution
/ref> yet they provide a home for 25% of all marine fish species. Reef habitats are a sharp contrast to the open water habitats that make up the other 99% of the world's oceans. However, loss and degradation of coral reef habitat, increasing

pollution Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...

, and

overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing Fish stocks, fish stock), resu ...

including the use of

destructive fishing practices Destructive fishing practices are fishing practices which easily result in irreversible damage to habitats and the sustainability of the fishery ecosystems. Such damages can be caused by direct physical destruction of the underwater landform and ve ...

, are threatening the survival of the coral reefs and the associated reef fish.

References

{{Aquarium Aquariums