I have 4 german blue rams in one of my community tanks (4ft) and they get on fine. Sure, the males and females fight with each other but that's
only because they're breeding machines just now.
They'll generally leave anything else in the tank and all the other fish leave them, too. One thing though, one of my pairs have successfully spawned
AND the eggs have hatched and they are now patrolling their little 'nest' like Mr T on acid. Anyone (or anything!) comes too close they'll get a swift telling
off and the male in particular will take on any fish that comes too close - even the large angels who are 5-8 times his size!