The key is having a proper number. As long as you stock about 12 dems, you can usually mix them okay. Or you could do a species tank with a group of a dozen, in a 33+gal tank. Before moving them to their current tank, I had a group of 6 in my 55gal mbuna community tank. They lived 'peacefully' (as far as mbuna go) with cobalts, labs, estherae, polits, 2 species of afra, kenyi...