Clownfish or anemonefish are fishes from the subfamily Amphiprioninae in the family Pomacentridae. About twenty-nine species are recognized, one in the genus Premnas, while the remaining are in the genus Amphiprion. In the wild they all form symbiotic mutualisms with sea anemones. Depending on species, clownfish are overall yellow, orange, reddish,green, purple, blue, hotpink or blackish, and many show white bars or patches. The largest can reach a length of 18 centimetres (7.1 in), while some can be as small as 10 centimetres (3.9 in).
In the aquarium......
Clownfish are now reared in captivity by a handful of marine ornamental farms in the USA, Clown fish were the first species of Saltwater fish to successfully be Tank-raised. Tank-raised fish are a better choice for aquarist, because wild-caught fish are more likely to die soon after purchasing them due to the stress of capture and shipping. Also, tank-bred fish are usually more disease resistant and in general are less affected by stress when introduced to the aquarium. Captive bred clownfishes may not have the same instinctual behavior to live in an anemone. They may have to be coaxed into finding the anemone by the home aquarist. Even then, there is no guarantee that the anemone will host the clownfish.
When a sea anemone is not available in an aquarium, the clownfish may settle in some varieties of soft corals, or large polyp stony corals. If the fish settles in a coral, it could agitate the fish's skin, and, in some cases, may kill the coral. Once an anemone or coral has been adopted, the clownfish will defend it. As there is less pressure to forage for food in an aquarium, it is common for clownfish to remain within 2-4 inches of their host for an entire lifetime.