Ok, Maybe a large Naso....
Bh, IMO and experiences,,,,,only place fer a tang is in a reef tank,so it can "graze" ALL day.i would never subject a tang to a FO or mebbe even a FOWLR tank. as a diver/ex-collector-prior LFS owner, all the many tangs i've seen on da reefs, spent their time :
feeding,pooping , feeding , making lil tangs,feeding,pooping , feeding,feeding,,,repeat,,,,ya get the point,,,,
tangs have a short digestive tract, food in, fast out,a normal FO tank will never,IMO ,give a tang enuf food availabilities to survive for long term,,,
just my opinion/experience,,,
my tangs in my reef tank do well, due to being inna reef tank , plus the fact that i also feed them like there is no tommorow,,,
just trying to help bro!