Also get some Repashy Super Gold. They love that too.
My favourite food, especially for grooming young goldfish is blood worms and this Hikari food
https://www.aquariumcoop.com/collections/fish-food/products/saki-hikari-fancy-goldfish
My current goldfish are eating the Repashy, Sera pond food, Hikari Fancy Goldfish, Xtreme Big Fella, Bloodworms, Southern Delight Fancy Goldfish, and lots of duckweed. I have 23 goldfish and they’ll all always eat all of the above (and generally anything else).