I have several of these I used to keep together until the Dominant one started beating the others up I have these all in 4 different 150g tanks.. They are all 4-6" long and I keep them with:
Tank 1- Hoplarchus Psittacus, Banded Silver Dollars, 4 line Pictus cat
Tank 2- Syniplsums, Convicys, clown loaches
Tank 3- Rainbow wolf fish, tiger botia, royal pleco
Tank 4- Super red Sevrums and Nics