It's so nice to see someone who will actually keep and take care of the fish they buy. I have so many people that drop off fish (and animals) at my store. "He got too big", "I'm allergic"(something you should find out before buying a pet. You can go to the store and hold them first.)"He/She doesn't take care of it anymore." That's my favorite, did you really expect a six year old to clean out there hamster cage every week!? I'm sorry, I kind of got off the subject. It's just that it's nice to see someone looking at thier fish as actual pets, not just a fish. And you didn't do anything wrong HE'S a RED DEVIL! Try decorating with actual rocks more and PVC pipe. They love to swim through them. Have you tryed a large catfish with him, or large barbs? They aren't competion to him so he might leave them alone.
Good Luck!