The previously mentioned pellets are all just fine for your rays. Remember, patience. They will eventually eat pellets.
I heard a small little (true) rumor that Purina is in the development/testing phases of a new pellet for aquaculture use.........I am anxiously awaiting the ingredients list and prices.
SC, when and if you do try to get the pups on pellets, try basting the pellets in a "worm gravy", that is, mash up the worms etc into a paste and let the pellets soak in the paste for 5-10 minutes, turn off the filters and feed. The remaining pups here are eating pellets on a regular basis because I did this gravy method. -FM