Yellowfin Surgeonfish (Acanthurus xanthopterus)
Also known as Curvier's Surgeonfish, Doctorfish, Lancetfish, Purple Surgeonfish, Ringtail Surgeonfish, Ring-tailed Surgeonfish, Thorntail, Thorntail Fish, Yellowfin Surgeon, Yellowmask Surgeonfish
 
Found in schools over sand slopes of deep protected bays, lagoons and outer reefs.
They feed on filamentous algae, detritus, pieces of fish and hydroids.
Juveniles found over surge zones of protected inshore waters.
Often curious towards boats and divers.
Length - 56cm
Depth - 1-100m
Widespread Eastern Pacific, Indo-Pacific