Thats a tough one. Marine fish dont grow to fit the size of the tank their in. I dont think they will reach their full max size in the vast majority of home aquariums......but I take the max size as a rule when choosing fish for my tank. So if a fish has been reported to reach 9-10 inches in the wild, I plan for that to be able to reach that size in my tank. Overcrowding in home aquariums is a real problem. Fish, (Tangs and Angels especially) get real snotty real quick when they feel crowded. Remember, its all about available resources. In the wild, those that dont or cant defend what theirs, (food/shelter) have to go elsewhere to look for it. And while their busy doing that, its quite possible they become food for someone else.....so their behaviours are hardwired into their brains for survival. You feeding them three times a day, and them learning to associate you with dinner, doesnt erase the million or so years of genetic imprinting on behaviour for them. Too many fish in the tank or too small a tank for a larger fish means hostilities will erupt....
Not trying to sermonize to you, but its something I see here fairly regularly...
Nick