OK I will 'splain this to you... And I will use "Finding Nemo" as my demonstration
Yeah, I know...
Dori...Her FIRST words..."LOOK OUT!!" Do you remember where she was and what she was doin'? She was not in the reef but just outside, cruisin in the more turbulant current. Tangs, all tangs, not just blue hippos are reef safe, but they do not live on the reef itself. Reef fish have a little hole they call home, and they roam around all day lookin for food and darting back into their hole (or anemone) when in danger. They have the whole ocean, but they remain in a small area. Tangs on the other hand were "built for speed" (also from Nemo). They tend to freak out when confined, and if a problem arises, that's usually the cause (to small of a tank).
Now a million people are gonna tell you how happy their tang is in their 55 (or smaller) but they obviosly have nothing to compare it to. Because a fish can simply survive, does not mean that he LOVES his environment.
LET THE FLAMES BEGIN!!!!!!