As for another big fish, I'd definitely go with pearl gouramis. Quite a docile fish that will tend to keep to itself if your tank is the right size. . As for German Blues, I have a 55g stocked with 2 males and 3 females, 10 tiger barbs, 6 green Cory, 8 bloodfin tetras and 6 mon tetras. Though the GBRs have paired off, they're not necessarily aggressive. They like to show off to fish they can get away with doing so, like my lemon tetras, but they don't nip or hurt them, only chase every once in awhile. If you kept them with angels, I doubt that they'd do a thing unless the angels tried to eat their eggs. You mentioned a firemouth - Pretty sure, given it is a decent size, would try to tear up your ram. Either way, good luck with the new tank!
