I think truly, any tank less than 300 is marginal for any Tang or Angel of the larger growing variety. But as said above, I expect most do what they want. Room for the fish to swim is important, food if supplied in abundance and or unlimited similar to a real reef is really not possible, and for what we do feed, filtration working at the max is very important.
Truth be known they should all probably stay in the sea if we were absolute stewards and really considerate of oceanic life....
But then again we would never learn anything about other life forms, no science no discovery... I don't know, who's to say, are we hobbyists, scientists, those who speak for animal protection and preservation?
Personally I enjoy the science and discovery, and couldn't say I don't enjoy just watching them float around...... What's important is " man's got to know his limitations", a little Clint Eastwood advise.
I feel Lee is a mentor for me and we have never met. His advise is generally beyond reproach, but I don't always listen to everything and sometimes stray from advanced knowledge.
Computers have given us an incredible resource of information. Take it all in, pick and chose, but most of all have a good time