When I had Malawis, I had them in a bare tank for a week while I was revamping my main tank.
They still fought.
I think it's in their nature. Yes, if there is no decor to mark out a terratory, it may may some of them calmer. But there are other factors as well.
African cichlids are way different.
I have never had luck w/ keeping CA cichlids in a bare tank. I think the more they see each other the worse it gets. I have added hiding spots and I have no aggression at all.
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