The clownfish, or anemonefish, are the subfamily Amphiprioninae of the family Pomacentridae. Currently 27 species exist, of which one is in the genus Premnas and the rest are in the subfamily's type genus Amphiprion. Native to wide ranges of the warm waters of the Pacific and Indian oceans and the Great Barrier Reef; some species ranges overlap others. Clownfish are not found in the Atlantic Ocean. Clownfish live in a mutual relationship with sea anemones, or in some cases settle in some varieties of soft corals, or large polyp stony corals when an anemone is not available in an aquarium. 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. Clownfish live in their anemone in groups. Usually a female lives with other males. When the dominant female dies, the head male changes sex and becomes the female.
(Courtesy: Wikipedia)