The butterflyfishes are a group of conspicuous tropical marine fish of the family Chaetodontidae. Found mostly on the reefs of the Atlantic, Indian and Pacific Oceans, there are approximately 120 species in 10 genera. A number of species pairs occur in the Indian and Pacific Oceans, members of the huge genus Chaetodon. Butterflyfishes look like smaller versions of angelfish (Pomacanthidae), but unlike these, lack preopercle spines at the gill covers. Butterflyfishes mostly range from 12 to 22 cm (4.7 to 8.7 in) in length. The common name references the brightly coloured and strikingly patterned bodies of many species, bearing shades of black, white, blue, red, orange and yellow. Their deep, laterally narrow bodies are easily noticed through the profusion of reef life. The conspicuous coloration of butterflyfishes may be intended for interspecies communication. Butterflyfish have uninterrupted dorsal fins with tail fins that may be rounded or truncated, but are never forked. Frequenting waters of less than 18 m (59 ft), butterflyfishes stick to particular home ranges. They are territorial, forming pairs and staking claim to a specific coral head. Their coloration also makes them popular aquarium fish.