[Nemo]

How about we forget talking about the size of tanks, I have seen plenty of large tankss 150g + that are so full of rock and corals that the fish have bo room.
I run a 140 g with about 100 lbs of rock, there is a ton of room for the fish to swim around in, and they use it.
Just to add to the the crap for the tang police I have a regal, sail fin, yellow, and powder blue. And they have more swimming room than some of the 200 g+ tanks I have seen.
So I think it would be far more important as to how much crap you keep in your tank rather than size, of course there is an expeption to every rule, I would not try and keep a tang in a 50 g even if I had no rock in it.
And like Brad said you want to get right down to it, the best thing is to not keep fish or corals, let them be in the ocean. So for all of you who are the self proffesed tang police, sell off your equipment and contents and join some bleeding heart group to stop the sale of all fish. Stop being too faced by keeping an aquarium

JMO