NEVER buy feeders they are extremely bad fish food because they have no protein and sometimes even carry harmful parasites which can kill
your fish. Some parasites can block the vitamin c from going into the fish which is a very important vitamin.
Say you have carnivores that will only eat live food then i would starve the fish and introduce tilapia, silver sides, bloodworms, etc.
But for pellet you can buy New life spectrum or Hikari.
What fish do you have?
p.s there are basically no sites that you can buy feeders from.