That's too many cichlids for a 55 gallon. In general, dwarf cichlids are rather peaceful, but they are still territorial, especially once they pair off. A good rule of thumb for most cichlids is to have at least 10 inches of space for each inch of total length for a pair. So a single pair of 2 inch Bolivian "rams" (M. altispinosa)should have at least 20 inches of space for their territory. Two pairs would be the max for a standard 55.