what i would do is not get the yellow labs and just get a large group of saulosi, i have a tank like this and it is great, the males are blue and lback and the females are all yellow so you would still get 2 of the best colorations in mbunas and would have no worry about hybrids, id get 3 males 12 females possibly a few more females if oyu want, saulosi are great fish, although if you want labs go ahead and get 1m 5f saulosi 1m 5f labs, although with a setup like that youd have all yellow fish with one male saulosi