they'll pretty much all interbreed. the best thing you can do is get fish that dont resemble one another, are from different genus's, and try to make sure you have good male to female ratios for each species youre keeping.
I think that even ones that don't look alike when they get desperate they will breed with any female regardless of what she looks like... best bet if you don't want hybrids... all male tank.
A good male to female ratio and fish that look very different will prevent hybrids. Keeping fewer species with a high female ratio is a safe way to stock mbuna. For example a lab/demasoni tank is a great place to start. It makes a beautiful display tank and the species are highly unlikely to breed with one another. 12-15 demasoni with 6-7 labs, the fewer males the better.
A good male to female ratio and fish that look very different will prevent hybrids. Keeping fewer species with a high female ratio is a safe way to stock mbuna. For example a lab/demasoni tank is a great place to start. It makes a beautiful display tank and the species are highly unlikely to breed with one another. 12-15 demasoni with 6-7 labs, the fewer males the better.