Yellow labs are robust enough to mix with the meanies, yet gentle enough so that they won't bother anything else. You really are not limited in what you can put with them, unless you get a rogue lab. There are no red mbuna. Closest is the red zebra, which isn't red. You could mix red empress with them if you want to try a hap. Need a 75g tank or so. Blue fish go well with them. A dozen demasoni, afras or even sc. fryeri. Some of the "red" peacocks (more of an orange) are also nice, but they've been bred out so much the quality of the stock widely varies. There are some diet issues to deal with in mixing mbuna with haps or peacocks, but it's nothing you can't overcome with a balanced food. Some people give their haps and peacocks strict veggie diets to help with color.
