I have a 380L malawi/mbuna setup which houses both peacocks and mbuna, apart from one dominant male mpanga being top dog over the sub dom male I have no aggression in the tank at all, even when the dom has a go at the sub dom it`s not bad or nasty aggression. You could have a mix but as with all fish it may be a case of trial and error which is something a lot of us experience.
The 'most peaceful' mbunas that I have so far experienced are: elongatus neon spot, socolofi, yellow labs, white labs. Ndumbi red tops are nice but can be aggressive.
Aulonocara/Peacocks can be just as aggressive as the mbuna sometimes and if you have a tank of just peacocks they`re very likely to cross breed. There`s no reason why you couldn`t look at having a mbuna setup that includes 2 very different looking pairs of peacocks but you`d be better off googling for some different types and then asking here about the aggression level and compatability of the fish that you like and might possibly look to keep.
Some important issues relating to the malawi/mbunas is to overstock to cut down on aggression, stock a ratio of 1 male per 2 or 3 females of each species, stock with different looking species to limit the possibility of cross breeding and have very good filtration to compensate for the overstocking.
Good regular water changes of approx 50% per week is good for ensuring the health of your fish, healthy fish goes a long way to give you a good amount of colouring in the tank too
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