i have that same combo in my 75. female jag n dempsey. had them when they were about 2 inches. theyre both around 5 inches now after 4 months eatin pellets, shrimp, flakes, blood worms, night crawlers, and random bugs. dempsey is slightly longer and wider girth. dempsey is the dominant 1 but isnt over aggressive with any of the other fish. jaguar likes to hide and prowl around the caves i set up. no problems between them at all as of now. take is perfectly balanced. i also have a powerhead so the fish can swim in the current if they like