I have a jewel in a SA/CA tank setup the jewel is the quietest one in the tank it doesn't pick fights with the other fish, pretty much stays to itself. I do know though if i put another one in there their aggression level will go up. Mine is about five inches long. I have with it a JD, GT, RT, nicaranguese, bucktooth tetra, convicts(blue/black) an oscar and green severums. The only one being picked on is the Oscar. The bucktooth tetras can live with piranhas and they stay small so might be a good choice to have a couple in a smaller tank. Hope this helps