Rays eat like crazy, so play around with the amount of food till you give them enough. That poop is not normal looking at all. Should be a dark brown coil. I'd treat with prazipro to be safe. I've found to get great growth and have fat rays I feed chopped nightcrawler, scallops, shrimp, and tilapia in about equal proportions. My rays are very thick. A good way to tell if a ray is really healthy is that it's back should be as high or higher than it's head. If it slopes down from head to tail you need to feed more or treat for parasites. Those rays look pretty skinny to me.
