Also known as Doctorfish, Lancetfish, Olive Surgeonfish, Orangeband Tang, Orange-banded Surgeonfish, Orangebar Surgeonfish, Orangebar Tang, Orangeblotch Surgeon, Orangeblotch Surgeonfish, Orangeblotch Tang, Orange-ear Surgeonfish, Orange-epaulette Surgeonfish, Orange-epaulette Tang, Orangeshoulder Surgeonfish, Orangeshoulder Tang, Orange-shouldered Surgeonfish, Orange-shouldered Tang, Orangespot Surgeonfish, Orangespot Tang, Thorntail, Thorntail Fish.
Found singly or in small schools in areas of mixed bare rock, rubble and sand over seaward reefs rich in algae growth.
They feed on filamentous algae and detritus.
Juveniles all yellow found singly or in schools over protected bays and lagoons.
Length - 35cm
Depth - 3-45m
Widespread East Indo-Pacific
Surgeonfish have a blade like spine in the tail that points outwards when bent, unicorns have two hook-like plates along the tail, these are used for defence and are as sharp as a surgeons scalpel, hence the name "Surgeonfish".
Some species are venomous. (edit) Ref: https://www.fishbase.se/summary/Acanthurus-olivaceus