theres not very many fish you can mix with a Jag. It really comes down to the personality of the fish. The Jags natural behavior will start to show around 7"+. In my tank I have a Jag and 2 oscars and a male convict plus 2 plecos. The Jag seems to be a grumpy fellow and doesnt like any fish around his flower pot. Their has been some aggression but just getting in eachothers face to challange one another, nothing serious. I would say to find something that wont get eaten when your jag gets monster size. My convict will one day be a tasty snack for my Jag if the con keeps provoking him. Good luck and let us know what you decide to go with!