From my previous experience (albeit limited, only had 6 for about ~9mos) they do well with other small semi aggressive but quiet characins like
Roeboides and large
Crenuchus. NO EXODONS! Exodons just beat the living hell out of them and a few exodons can kill off a shoal overnight (ask me how I know
)
Cichlids, I had the most luck with larger dwarfs and dwarf pikes (if you see the cichlids breed make sure there's enough space because they will hammer the
Charax in smaller tanks). Larger more aggressive cichlids just treat them like unusual target fish and they're usually dead in a day or two - they're more delicate than your typical barb/danio dithers.
Almost any bottom dweller that can't eat them/vice versa will work well, I had mine with
Brochis sp. and some large
Microglanis iheringi. They seem to kinda pick at other characins (as most tetra type fish do) but largely ignore anything dissimilarly shaped that's too big to swallow. While I've never actually tried them together, I think thatthings like
Ctenopoma acutirostris and
Monocirrhus polycanthus would work as would
Anostomus and/or smaller
Leporinus sp.