Hello all, I'm new to the site but not to monster fish. A few years back I had a 30" Arowana and I've also had piranha, pacus and oscars. Currently I have two arowanas about 7 inches long that I recently got about a month and a half ago at approximately 6 inches. They are in a 200 gallon (84x24x24) tank along with softshell turtles, catfish, a royal clown knife fish, and some peacock cichlids. I have not had any issues with them attacking each other. They do chase each other around sometimes but not bad at all. My royal clown and the cichlids are the most aggressive of the group. I can say that my juvenile arowanas get along good and I'd like to get a third of similar size for when I upgrade my aquarium. I never would have thought that having only two juvenile arowanas in a large tank would be an issue as mine have been doing fine so far.