Annoying Aggression!!!!

[vao71]

Hi guys, I post way too many questions on this website but this problem is just annoying me. I would say I'm a rather experienced stingray owner, I've kept them before. The ones I've kept are teacup (reticulated) stingrays. Anyway why, why, WHY, WHY!!!!!!!!!! is there always that one #@%#&$@#% fish that is always biting the stingray!? I've had this before with my first stingray and her disc was a mess from all the aggression towards her. I removed all those fish and it seemed to kind of swell the problem. I'm on my second one and shes in a 125 and now its my tiny discus that is always looking at her like a moron and just biting her before she runs off just to see the discus do it again. It's so frustrating to see you're two favorite fish constantly going at it. I wanted to make this tank a discus tank but I'll pick the ray over the discus. Do you guys know of anyway to stop this nonsense?