Acanthuridae is the family of surgeonfishes, tangs, and unicornfishes. The family includes about 80 species in six genera, all of which are marine fish living in tropical seas, usually around coral reefs. Many of the species are brightly colored. The distinctive characteristic of the family is the spines, one or more on either side of the tail, which are sharp. The dorsal, anal and caudal fins are large, extending for most of the length of the body. The small mouths have a single row of teeth used for grazing on algae. Surgeonfishes sometimes feed as solitary individuals, but they also often travel and feed in schools. Most species are relatively small and have a maximum length of 15–40 cm (6–16 in), Adapted from Wikipedia.