So i picked up a new motoro stingray for my 180 gallon aquarium this past Saturday. He is very big (around 12 inch disk) and he appeared to be very healthy in the store, eating and very fat. He still has yet to eat in my tank and I am starting to get concerned. He was totally buried for the first day or 2 but now he seems to be starting to come out a bit more today. His belly appears to he a bit red in some spots which concerned me, however the ammonia level appears 0 so I dont think it could be ammonia burn. I know that my sand it fine for rays so that couldnt be causing it either. The heater is in the sump. The nitrites are at 0. Before I added him to the tank the nitrates were 20-40, but they since have raised to 80. Should I do a water change right now? Also i forgot to add, the water temperature is 80. Also, he APPEARS to be breathing normally. This ray was $300 so I cant afford to loose him. Any suggestions?