ok I was planning on only keeping one of them,with the balas and eel not,both so I guess I will pick one of the 2 haha !
A 150 would be the bare minimum for a Flagtail and a datnoid. Only problem I can see is that flagtails tends to grow much quicker than dats, and flagtails can be punks. On the other hand, dats can be pretty bold themselves.
My understanding is that Thorichthys species like Firemouths live in groups.
Also, it's a Central American fish and may not thrive in the same conditions as an Oscar. Of course these are all captive bred, so maybe it doesn't matter so much.
6" if you take good care of themDenison barbs maybe what's the max size on those?