While I agree that many fish will outgrow tanks that are too small, there is also evidence to suggest that some fish get"stunted" by closed systems,especially if too small. In corresponding with several marine biologists on this topic several months ago, many of them claim to have done research which suggests that many species, large angels in particular, seem to "stunt" in comparison to natural size . Particular reference was made to emperor and french. You will also notice that many aquarium books will refer to captive or tank size VS. ocean size. They will also make statemnts like..."rarely observed" in the aquarium over such and such size which is always less than natural adult size in the wild. This is also recognition of some stunting that does take place in the aquarium.
This info. should not serve as a reason to put large fish in small tanks. WE should strive to give all of our aquatic creatures the best artifical aquarium environment possible. This does not include cramped quarters.