A ten gallon tank is nowhere near big enough for one P. crabro (bumblebee), let alone 3. A good sized male will get to at least 8" and I've seen 9" ones. They get extremely aggressive! You really should have more females than males. Males will try to get a female to spawn all the time, and when she doesn't, he'll turn mean on her and most likely kill her. This is one of the larger mbuna types and should be in a 75g +++ tank. I think that would be the smaller sized tanks to house a crabro properly. They can be bred at a smaller size of course; just like any other mbuna.