He is the biggest by far. I have a 6in red devil/midas, 6-7in ?starlye?, and a 3in black convict in the tank. The oscar is pushing 9in and gets a long fine with both devil and convict. The other one tries to pick fights but almost always backs off. Best chance it is him. Do you think he'll be alright? He's quarintined in my 10 gallon right now.