I have a breeding pair of cons now with fry in a tank with silver dollars, a lone angel fish ,and 4 other adults convicts . Have also had a pair with two firemouths in the past. The firemouths can take on the cons for sure. You may be in for some trouble, but I have found that the cons only chase the fish from their area while breeding and keep everyone away from fry. Fish retreat with no injuries. I have been breeding cons now for about two years. This was not planned!!! I have had atleast 1000 convicts in this time period. I have 4th generation convicts now, all starting from a single pair. Once they start it will not stop. The babies will grow and mate , Their babies will grow and mate!!!
My firemouths actually intensionally bothered my cons while they were breeding. The cons fought but they did no harm to one another. The firemouths will display a cool brite red color and expand their mouth and gills when provoked ,thus giving them their name. The firemouth may not bully others like a convict, but is its equal in battle.