If you are a "purist", then the answer is no - if you are a typical fish keeper, like most others and myself, then what the heck! I have a few Tanganyikans in my 90g show tank with a majority of mbuna, and they are fine. For my breeding tanks, i don't mix lakes and very rarely species. If you are just starting out, I would suggest sticking with one or the other, until you get a "feel" for their behavior unique behavior and dietary needs. Best of luck!