Fish

A fish is any member of a paraphyletic group of organisms that consist of all gill-bearing aquatic craniate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups. Most fish are ectothermic ("cold-blooded"), allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature. 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 the abyssal and even hadal depths of the deepest oceans (e.g., gulpers and anglerfish). With 33,100 described species, fish exhibit greater species diversity than any other group of vertebrates.

Fish are an important resource for humans worldwide, especially as food. Commercial and subsistence fishers hunt fish in wild fisheries (see fishing) or farm them in ponds or in cages in the ocean (see aquaculture). They are also caught by recreational fishers, kept as pets, raised by fishkeepers, and exhibited in public aquaria. Fish have had a role in culture through the ages, serving as deities, religious symbols, and as the subjects of art, books and movies.

List of marine aquarium fish species

The following list of marine aquarium fish species commonly available in the aquarium trade is not a completely comprehensive list; certain rare specimens may available commercially yet not be listed here. A brief section on each, with a link to the page about the particular species is provided along with references for further information.

Angelfish (large)

These big beauties are considered to be quite hardy, but because of their size may present a significant challenge to the potential keeper. They need huge aquariums, up to 180 gallons to house one for its entire lifespan. Two angels might be kept in the same aquarium provided it is a large aquarium, they are properly acclimated as juveniles, and they have very different colouring and body shape. However, because all Angelfish have essentially the same diet, mixing them is a feat that should be left to only advanced keepers. None are reef safe, and a potential owner should be aware that they need to have plenty of vegetable matter in their diet. They undergo major changes in colouration while maturing, and unless specified given descriptions are for adult specimens.