I think its a bit risky to try that. You could get some really out of control aggression, but haps can be quite different from each other so you may get away with it.I have a mixed gender tank. Mostly male peacocks and haps, however there are 2 female fossochromis rostratus. Those fish breed regularly. I know people like the all male look, but I would encourage you (if you can monitor it and try to stick with ones that are different) to have some females if the tank size/tankmates are suitable. Without females you will never get the color on some fish (granted there is a solid argument that doing this would cause other fish in the tank to not color as much).