How many of the Geophagus species could I reasonably fit in a 55g? I currently have 3 juvenile Geo. jurupari, and I've like to add a couple of Geo. "Red Head Tapajos" to the tank. Is this feasible, considering their adult size? It's a well-established tank with lots of large driftwood, rocks, and plants for hiding. There's some little community fish in there, but they could be moved elsewhere if need be. Thanks!