First Off, a jaguar is not good cichlid to attempt a community tank with. I know to you a 125 is a huge tank. But as far as mixing large, predatory, CA cichlid it is the bare minimum. Some questions for you. Is you jag a Male? Do you have previous experience keeping a larger predatory cichlids in a community system? Do you have working knowledge of how to curb cichlid aggression by using rock work, decor and Line of site surpression? If you never hard this before don't let it scare you off it's not that hard. I keep a male jag, male trimac, male midas, in a 265 with NO problems. In fact my midas was just at a show with not even a spit fin. It can be done. I'm just trying to get a feel for your experience level and what we are dealing with, so I'm not wasting time telling you things you already know. I can tell you that a male jag can and may take over a 125 gal. tank with no problem.