Help Teacup Stingray Acting weird!!!

[phongnguyen123]

Hey i have a male teacup stingray i had him for about almost 2 years, but today he started acting very weird. He usally eats 3-4 massivore pellets at one feeding time, 3 times a day. and he would swim all over my tank but recently he stopped swimming around my tank and all he does is sit still or try to swim up my fish tank glass. Im not sure what the problem is?? can anyone help me? i have him in a 60 gallon bowfront with black carib sand and a couple amazon swords and anubias. he currently lives with a couple discus around 6? i got 3 hang on aquaclear 50s filter long air rod and everything i change my water 30% every 2-3 days. i have a heater the water temperture is always at 84-83. All my fish is doing great except the stingray is just acting weird swimming up the tank glass all day. like i see him doing it for hours just swimming up the glass. HELPP!! I really dont want to lose this sting ray he is about 6-7 inch and is breathing really fast.