Distinctive Characters: Dorsal fin with 6 spines and 26-29 rays. Anal fin with 2 spines and 27-30 rays. Pectoral rays 17-18. Body depth varying from 2.0 in standard length of subadults to 2.75 in adults. Dorsal profile of head sloping and smoothly convex. Caudal fin emarginate in young, truncate in adults.
Colour: Dark brown to pale bluish grey dorsally, yellow brown ventrally. Edges of opercle and preopercle often dark.
Habitat and Biology: Common in deeper waters up to depths of 150 m; often in large aggregations. Feeds on larger components of the zooplankton such as crab larvae, arrow-worms and pelagic tunicates.
Remarks: Males of Naso hexacanthus show a large pale blue area on upper head and dorsoanterior body and some pale blue vertical lines and spots anteriorly on sides of body during courtship.