Hey guys, I'm actually new to this forum. I've been just skimming through a lot of these discussions, and I'm glad to be a member. I have a piranha tank and I also have a south american cichlid tank. Through my experience I must say in your particular situation, I really dont see one killing the other, unless space becomes an issue, or even hunger. But as the jaguar cichlid matures, the piranha will definately start having problems, becuase the jag becomes more territorial, and they usually live in solitude. But if they grow with each other for a great time period their might be a chance the piranha will survive. If the two as you said are doing fine now, the jag should have no problems in the future, becuase its growth rate and aggresion is greater than the pirahnas. I've had cichlids mixed with pirahnas in a tank before during my earlier years as a hobbyists and they all did perfectly fine; but I don't recommend it. If you have someone who can by the jag, then sell it, because it seems like you want a few pirhanas in your tank anyways.