I've had tons of platies over the years. Now I have four in a 65g with a school of ten bleeding hearts and a L204 pleco. Three of them love the world. They swim with each other and even love to swim with the bleeding heart school around the tank. The other one... not so much. The angry yellow platy spends its time patrolling the bottom level of the tank. Thankfully it is confused and a little scared of the pleco, but if anyone else comes around, he chases it off, platy or tetra. The only time he goes to the top half of the tank is during feeding or when no one is down there to bite. In this case, he swims up to nip someone before swimming back down. No one ever retaliates or seems to care, but this is one angry platy. I've never had one like him.