- English Name : Sleek unicornfish
- Local Name : Dhalhu neiy thunbi
- Size : Max. 75 cm
- Family : ACANTHURIDAE
- Order : Perciformes
- 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.
- Distribution: Indo-Pacific.
- 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.