Acanthurus tristis (Tickell, 1888), the Indian Mimic Surgeonfish, like A. pyroferus also imitates the dwarf angel Centropyge eibli.
Just to buttress the discussion, these tangs, tritis and pyrferus are very similar. I am not suprised that my search came up with a misidentification.
Both of these images appear here
Acanthurus tristis - www.meerwasser-lexikon.de. May be a post juvenile/pre adult stage with the stripes.
Both genus appear to be good reef candidates.
__________________

Currently tankless.
20 Gallon mini reef with mated pair of Maroon Clowns given to Rougiem!
80 gallon reef given to Rougiem/Wooster HS.