I am starting a 75 gallon australian rainbow society tank, any advice?

I enjoy australian rainbows. But I have had a bigger austalian rainbow beat up a different type of rainbow fish species. Are australian rainbow fish "territorial"? I have a banjo catfish in there with the 1 that I have started with. They seem to get along fine. I have alot of room and adequate filtration and cover. Anyone with experience in these fish?