If you are going with all Mbuna, they can all cross breed, but, I have a 75 gallon "community" tank with 4 Red Zebra, 5 Yellow Labs and 4 Kenyi, one male of each species and the rest females; they have yet to cross breed. My experience has been that they prefer to breed with their own species if possible, but, as I stated before, all Mbuna can cross breed. You could put a few male peacocks in with them as long as you don't put in any duplicates or look-a-likes; Labs are more tolerant, less aggressive than most other Mbuna.