In my case, i've been able to keep them with some South Americans and Cyrtocara moori. While they were still juvies, I kept them with Orange chromides and they did fairly well. They weren't overly aggressive, but they did a few chasing around.
Currently I have them housed in a 125. They range in size from 4-6 inches. I have my Paretroplus Dambabe, Paretroplus Maculatus and Paretroplus Menarambo mixed in that tank, but in the future, i hope to separate them. A few other Paretroplus keepers have warned me that they have a high possibility of interbreeding.
I also noticed that, the more of them that you have, the less likely they are to pick on each other.