The Lavender Tang, Acanthurus nigrofuscus, also known as the Brown Surgeonfish, has a disk shaped body, very similar looking to other Acanthurus species.  Adult coloration varies from a brown to a light grayish brown featuring a lavender color on the fins. When stressed or  displaying aggression, its entire dorsal fin and upper back lighten in color, sometimes becoming noticeably yellow. Also featuring blackish brown lips, its pale pectoral fins are narrowly edged in black, and at times, the anal fin is narrowly edged with white, with a crescent shaped caudal fin. On each side of the caudal peduncle is a single spine or "scalpel" used for defense or dominance, hence the Surgeonfish reference. The spine is folded down into a groove that is circled in black when not in use. Juveniles are brown to bluish black and have orange scribbles on the head that break up into spots as they mature.

The Lavender Tang  requires a tank with a moderate to heavy flow, creating currents to swim in. Being very active during the day, they require a large tank with plenty of open room to swim about while also providing plenty of live rocks and or Corals providing places to hide if frightened, as well as to sleep in at night. Lush natural algae growth in the tank is suggested in order for the Tang to be able to graze upon in between meals.