I've had very good results with growing out multiple species of Paratheraps in a 125--so far. Argentea, Regani, Zonatus are all famous for the kind of behavior OP describes. They're all at 4-6 inches now, the tank is getting very crowded, and I'm sure it's all about to get muderous at any moment. But, I think that multiple different species, crowding, and starting the fish together very young all contribute to the tenuous peace.
On the other hand, my son's tank is a 75, not really big enough to stock the same way, so we've gone with 2 Breidhori and 1 Zonatus, and 1 small Argentea, and when we add single fish of other species in there they get killed pretty quick. It just doesn't work the same. We've tried couple different types of tetras as dithers in there, that isn't helping much either. It's just a wierd situation in there. The fish never fight, everyone seems to understand the male Breidhori is in charge in that tank, but wake up in the morning, and something is dead or seriously beat up.
