Male yellow labs will have black lining the ventral fins, this is a pretty sure ID, an all male tank will fight some, these guys are peaceful for a mbuna, not peaceful, that means they will still rip fish fin from fin, I have a dominate male who will kill any mbuna attempting to suit his females. I would shoot for around 10 fish to help spread aggression, similarly sized, somewhere in the 3 male to 7 female or 2 male to 8 female range. Breeding shouldn't be a concern, if you do not strip the mother and raise them yourself then hungry cichlids will make the fry disappear as fast as they appear. An all male tank could work, but one rogue dominant could put the rest in danger.
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