Generally it can work out. Depends on what haps and what mbuna....some haps get 18" long and some mbuna only 3". The small mbuna would eventually become expensive snacks. Keep in mind that most haps are carnivores so you'd need to get mbuna that are omnivores (there are a few carnivore mbuna). Then you could feed some vegetable matter along /w a little protein. Otherwise, herbivore mbuna could get "malawi bloat" and die. Lake Victoria cichlids would also mix.