There is no aggression and they are schooling together eventhough I heard they are only schooling when younger but then going their seperate ways. But they are being buds right now!Zoodiver;1071917; said:Pacu are actually a schooling fish by nature. They do better in groups. The down side is finding a tank big enough to keep them in groups. If you introduce sub adults to each other, there might be some aggression. It will pass with time.