okay stingray was eating fine the first week I had him. He was eating krill,shrimp and nightcrawlers. Now for the last 1-2 weeks he'll chew and attemp to eat everything but cannot swallow.I'm feeding pellets,frozen brine shrimp,frozen krill,frozen bloodworms and live nightcrawlers between blood worm size and 5 inch. water parameters are 0 ammonia, 0 nitrite ad 20 nitrate.Currently she's housed in 450 gallon with 4 other motoro stingrays all around 6-9 inches all other stingrays keep getting fatter. I feed 3 times a day and change out around 50-60 gallons a day with automatic drip.I'm starting to get concerned due to hip bones now petruding.There are no obvious signs of injury or disease.Ray is very active always swimming in current from filter.