mawv, I agree that tangs belong in the ocean, but all of the others do too, we keep them for our selfish purposes, It isn't much better for the rest of our fish either.
But really, tangs do love to swim, their passion is to roam free and keep going on and on forever more, but they can't do this in our aquariums.
Like was said in Finding Nemo, "fish weren't meant to be in a box kid, it does things to ya."(In the background the yellow tang is yelling, "bubbles, bubbles, My bubbles!")