Members of the surgeonfish family generally have a compressed body, a single dorasl fin, and a small mouth small with many small teeth. Many are algal grazers, some feed on plankton. There can be marked colour change from juvenile to adult. All have spines near the tail. The spines are often surrounded by a warning patch of bright colour. The Family Acanthuridae consist of 3 sub-families:
a single, sometimes venomous, moveable spine on each side of the caudal peduncle, used for fighting and defense.
several fixed, often curving, defensive spines
several bony peduncular plates with a short fixed spine.