Surgeonfish come from the family group Acanthuridae, which means "thorn tail". This apt name describes the rather nasty sting in their tail – the most distinctive characteristic of these fish is the sharp blades which sit on either side of their tails. Some fish have just one pair but others have several. No matter the number though, all these blades are razor sharp and are used to defend territory and themselves against each other and predators.
Apart from surgeonfish, the common names for fish in this group include tangs and unicornfishes. Tangs tend to be rounder rather than long ovals while unicornfish are longer. Some are easy to identify as they have a unicorn horn on their forehead.
Most fish in this group are small, between 15 and 40 centimetres long but a few will grow larger - the whitemargin unicornfish is the largest species in the family, reaching up to a metre in length. Surgeonfish feed on algaes and detritus and often feed alone, but they are sometimes seen feeding in schools, which is thought to be a defense mechanism against smaller, territorial damselfish.