You don't have to replace the Tapajos. The specs only get to a foot and mostly pick on each other. Be careful not to keep them with other robust piscovores as they have very weak jaws and can end up dislocating their jaw if they lip lock. I lost my dominant male spec when he lip locked my hoplarchus psittacus.
I like the idea of the Specs with the Geo red heads as they are both found in the Rio Tapajos. I think Caquetaia are an under appreciated group of fish.
Lastly, umbees are now classified in the kronoheros genus now.
