Blue tang (Acanthurus coeruleus) shoaling over a coral reef. This fish, also known as the blue surgeonfish, inhabits the tropical and subtropical coastal waters of the Atlantic Ocean, from as far north as New York, USA, to Brazil. It is also found around mid-Atlantic islands such as Ascension. It feeds almost exclusively on algae and can reach a length of nearly 40 centimetres. It gets the name surgeonfish due to the extremely sharp spines on the base of its tail, which can inflict painful injuries on people who handle the fish. Photographed off Bonaire Island in the Netherlands Antilles, in the Caribbean Sea.