Sorry if I came off harsh, but was trying to make a point. I think if you want a yellow tang, and have the right filtration and set up you can get away with it. I dont see how a 55 gallon tank at 48x12x15 is going to be that much more different then a 90 gallon tank that is 3 inches deeper. You can get away with it a 4 foot 90 gal but not a 55 ?
I guess I didnt read the part where he had 20 other fish in the tank either, to see where it may be over stocked. Some places state that 50 gallon is all you need (*Link Removed*) and as others have stated, they have them in a 48 and such and never had an issue.
My point about nothing being large enough and somone tried to tell me I was wrong, you honestly think that a yellow or any fish for that matter only swims in one specific 80-100 gallon area of the ocean ? If he swims for a mile, its because that is what they want and need to do, then you would need a tank a mile long. Obviously if that was really how things were to be, this hobby wouldn't exist.
As far as the not being to aware of sharing a room is like. I shared a room, bunk beds with my brother from time I was old enough to be in a bed till he was 15 and he got of the room. Was never a problem, I know many who have kids who share a room, as someone pointed out here, it is possible. As for my kids, my two are 9 and half months apart, yes 9 and half months. Top that one, both born in same year. They are 4 and 3 now. They will have a sibling in 8 months or so, and they will have to figure out who wants a room-mate.
Again, I appoligize if I came off sounding rude, but was trying to point out if you feel that a certian fish cant be kept in a certian size tank, especially when the fish is far from full grown, then no tank is big enough for any fish.
Jeff