I take it they mean Apistogramma cacatuoides.
These are relatively peaceful cichlids and only grow to about 4inches.
I've never had any but know of a couple of people who've kept them in community tanks with no problems but thats no guarantee.
I wouldnt put them in with Malawis as they have very different requirements as the Cockatoos are South American Cichlids.
You can keep them in relatively small tanks 30g and upwards (maybe a 20g long) - i'd always keep them as a pair.
they are a fish i've always wanted but never had the room for another tank - well not yet anyway