Ok we gave you advice but you keep trying to change your stocking by adding other aggressive cichlids. If you want advice, pay attention to it. Forums are not always right so information is not always true. You say a BP is not aggressive as a firemouth but you don't even have any experience on them yet. How do you know they are not? I would think the dithers would become food once the cichlids get big and if they fit in their mouths. In my opinion, a 55 is just too small for all three cichlids. Maybe if you got a 75, it can work.