[Diomedes]

Good point titus, but we cannot determine a Tang's happiness by drawing parallel lines to our own personal experience...I know a few people who would take what you shun. But that doesn't mean a fish is happy (or not) in any system. And your calculations, obviously more complex than mine are really interesting. But I still don't understand them...
I am not here to say that a given small tang is happy or not in a 33, nor did my calculations. They simply showed that a world expert gives his MINIMUM tank size as less. I'll bet he prefers more space though...
Second, I did not mean to imply that fulfilling a tang's foraging needs etc. would also negate its needs for space. I guess it kinda sounds like it, but I believe that eliminating/changing these 4 needs also changes (not eliminates) their natural need for space.