Large earthworms (from angling shop), all sorts of sinking pellets but mainly massivore, frozen large krill superba, mussel, sprats, whitebait, lance fish and cockle (shell off).
I see a lot of people using bloodworms and I can only think these are suitable for pups.
My rays are around the 12" mark and the pup has been eating large fish from 7"' they cope with it easily.