Very nice Fug....I have always found the Geophagus brasiliensis are to rough for my geos and push them all around. What have you seen from yours ?
I've had no problems at all. I keep my 4.5" brasiliensis in a 120 gal with my gymnos. He's outgrown the others, but rarely does more than a little nip or brief chase, usually when there's food to scrounge. He's fine with the winter cool-down period as well, although the temp only drops to about 63F.
G brasiliensis includes several variants that could easily represent different species. They are poorly documented right now. Perhaps I just lucked out with the type I have.