my 75 red belly tank currently is stocked with, 3 red bellies, 5 ruby barbs, 5 cherry barbs, 3 x-ray tetras, and a roseline shark. I have almost never fed my piranhas live, and when i did try to i had to eventually scoop the rosy reds out of the tank because they piranhas would not eat them. So i think their diet of pellet food and frozen foods for 95% of their life have aided in being able to have other fishies in their tank. I've had this set up for like 6 months and havent lost any of the other fish, and I have added live plants to give the other fish someplace to chillax or possible escape the piranhas.