in my 75 gallon tank i have 1 gold severum and 2 keyholes...( can move the keyholes to my 50gallon is it doesn't work out) I'm going to the fishy shop tomorrow to get a parrot fish ...i would like to get 2 more smallish cichlids convicts or firemouths or 1 more severum which would be the less agressive and more compatible in my tank? Thankyou!