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I need to set up a tank that will house ONLY males. I have way too many right now.

What would be the best way to set this tank up to avoid too much aggression?

Lots of slate and no caves? Lots of slate and lots of caves? None of the above? etc?

For a male only tank go for as big a tank as you can, and i would put plenty of caves in the tank for the males, more than one per fish, so there are always free caves.
Some pieces of mopani wood is also good for hiding places as well as the caves.