I've had fahakas before. I was actually trying to place the puffer as a centerpiece along with some smaller african cichlids. That wouldn't work well with a fahaka (probably not), but might do ok with a pustulatus if I could find one.
As far as RTR, you can certainly see my confusion on the subject, right? I've seen varying tank sizes from 400-450-800-1000-and now 4500. RTR mentions a tank no less than 400 (in one of the links I posted earlier), Li$a a 450 for hers, Mike (I think you know him as arapaimag) has his in an 800 (not his 52k not his 15k), the ever popular 1000g that everyone throws out (clearly an arbitrary number), and now a 4500.
I'm trying to demonstrate a point that opinion =/= fact. People are very content to present an uninformed opinion as their own and not have any empirical evidence to support it. I'm not blaming anyone, I'm trying to get people to exercise their brains and advance the hobby. There have been several instances of a blanket opinion touted as fact, and the poster couldn't even say why.
Now, should an mbu be in a 375g tank? Who knows? Should any fish be in a tank? The fact that we keep any fish in a closed environment and call it humane is somewhat inhumane if you get down to it. But that is the hobby we love, and this is the nature of the hobby.