Brown Surgeonfis, Acanthurus nigrofuscus, also known as the blackspot surgeonfish, brown tang, dusky surgeon, lavender tang or spot-cheeked surgeonfish, is a species of marine ray-finned fish belonging to the family Acanthuridae, which includes the surgeonfishes, unicornishes and tangs. This species is a common and abundant fish occurring across a wide Indo-Pacific range. It commonly makes its way into the aquarium trade. It grows to 21 cm in length. The lavender tang is an herbivore that grazes primarily on benthic algae. In captivity, they will also feed on animal matter such as brine shrimp and mysis shrimp. pesce chirurgo Acanthurus nigrofuscus

Brown Surgeonfish – Pesce Chirurgo marrone – Acanthurus nigrofuscus – www.intotheblue.it
Acanthurus nigrofuscus has 9 spines and between 24 and 27 soft rays supporting its dorsal fin while the anal fine is supported by 3 spines and 22 to 24 soft rays. The dorsal profile of the head his slightly humped. The overall colour varies from brown to purplish to bluish-brown marked with small orange spots on the head and breast. There are small black spots at the base of both the dorsal and anal fins, these fins have a pale blue margin. The spine on the caudal peduncle is contained within a patch of black pigment. There may or may not be sinuous horizontal lines of small blue dots.

Brown Surgeonfish – Pesce Chirurgo marrone – Acanthurus nigrofuscus – www.intotheblue.it
Acanthurus nigrofuscus has a wide Indo-Pacific distribution from the coast of eastern Africa as far north as the Red Sea coast and south as far as far south as the Aliwal Shoal in South Africa, across the Indian Ocean and into the Indian Ocean as far east as and the Pitcairn Islands and Hawaii, north as far as southern Japan and south as far as New South Wales. This is a numerous and common surgeonfish that is found in small schools on sheltered coral and rocky reefs, frequently around isolated rocky reefs at depths down to 25 m.

Brown Surgeonfish – Pesce Chirurgo marrone – Acanthurus nigrofuscus – www.intotheblue.it
Although typically encountered in small groups it will form large schools in oceanic areas, as well as gathering in large spawning aggregations. This is a relatively small surgeonfish and may be dominated by other larger species but the large schools they form can displace other grazing fish.
(extract from Wikipedia)