First of all you're going to either have to lose the africans, or the americans. I'd say keep the americans (since I like them better) but you can keep more africans in a tank that size. Just admit that you probably won't ever have enough room for the dovii, or the oscars and get rid of them. You should decide between the texas, red devil, or jack dempsey. A single one will work fine in a 55gallon until you can upgrade but none of them well ever be comfortable in that tank, even alone.