Young rays can be very particular and when they are this thin it isn't the time to try to get them to start taking new foods. Our batray will only eat krill & ghost shrimp. We have offered her night crawlers & red worms on many occassions, she runs from them like they are poison even if we cut them up. We feed her twice a day and she is fat and sassy. She is a little over 8 months old. Load your pup up on ghost shirmp so there is an abundance in there. Once you get some weight on him they you can try feeding other things, until then use what you know he likes.