Surgeonfishes, tangs, and unicornfishes are members of the Acanthuridae family. They are distributed worldwide mostly in tropical seas. They have a deep compressed body with the eye high on the head and a long preorbital bone. The distinctive characteristic of the family is the sharp caudal spines of the tail, which are dangerously sharp. Their dorsal, anal, and caudal fins are large, extending for most of the length of the body. Their small mouth have a single row of teeth used for algae grazing. Many species have bright colors and are popular aquarium fishes.
Surgeonfishes are marine fishes usually found around coral reefs or over rocky substrate, generally at depths less than 100 m. They sometimes feed as solitary individuals, but they also often travel and feed in schools. Most surgeonfishes species graze on benthic algae and seagrass, while some species mainly feed on zooplankton or detritus. Surgeonfishes are able to slash other fishes with their sharp caudal spines by a rapid side sweep of the tail. They are pelagic spawners.
The family Acanthuridae is divided into 3 subfamilies with different caudal spine characteristic. The Acanthurinae subfamily with a single folding spine on each side of caudal peduncle. The Prionurinae subfamily with 3 to 10 fixed bony peduncular plates, becoming keeled with age. The Nasinae with 1 or 2 fixed peduncular plates, also keeled with age. There are 6 genera and 85 species worldwide. Malaysia has 5 genera and about 33 species.