250 litres. The references I have say 8" max, same as the scopas, and if he does grow too big, I can always pop him into my bigger FOWLR tank.
I want to try him in the reef tank because he has been picky about eating in the quarantine tank. I caught him locally, and in the tank he only eats algae off the rocks and glass. There is plenty of this in the reef tank, so he will do well if not picked on.