My Festae def runs my tank although he is not a "killer" the other fish just run from him. If he was not there I think I would have a few aggr issues, but he keeps everyone in line. I have a larger tank with some very aggr cichlids, but the Festae is boss of them all!!! In your case I think you could put in a Festae and then some, but later on I would be concerned with the Firemouth and maybe even the convict. Also, don't quote me as I have not had a Convict in any of my tanks in about 15 years... I think the females have the red color on them... not the males. Good luck and post some pics when you get it up and going.