Dark brown/blue to black, white tail with a yellow bar, white patch below the eye and a white ring around the mouth, yellow lines at the dorsal and anal fins and a yellow tail spine.
Christmas Islands to Indonesia, Micronesia and Hawaii, Southwest Japan to Australia and New Caledonia, Cocos and Galapagos islands and coast of Mexico. Inhabit hard substrate areas of clear lagoon and seaward reefs from the lower surge zone to at least 67 meters.
Up to 21cm.
It feeds on filamentous algae.
Territorial species. Known to hybridize with Acanthurus achilles.