I have had the geo, heck, and robert since September. They were all in the same shippment from Rapps and were all about the same size so maybe if they grow up together they will get along. The robertsoni ignors the geo and only during feeding does he chase the heck any at all. The oscar and severm keep them all in line however as the severm does not like the robertsoni so he has something to keep his mind on other that chasing the geo and heck.