But of course, mon ami!!! Didn't you know SNAILS are a favorite goldfish gourmet delicacy? Truthfully, I made the blunder of trying to keep apple snails with my goldfish in my teens. Came home a few times to find empty shells and happy, FAT goldfish...
Mine were too small when I had them with a snail. The goldfish ripped the guy out of his shell and pecked him to pieces. Never was able to eat him, though.
Goldfish will try to eat pretty much anything and snails are no exception. Larger Snails will be pulled out of their shells while smaller softer shelled ones may be swallowed whole. There are some species of snails that seem to have enough body armour to not be eaten, Malaysian Trumpet Snail or Melanoides tuberculata for example.
Ah, now I know what to do with my soon to be overpopulation of snails! Buy a goldfish and save on fish food too! (just kidding) But it sure would solve my libidinous snail population problem. Naw, it goes against my grain to buy a 30 gallon for one fish.....pretty as they are. Hmmm, maybe I can grind the excess snails up for crunchy foie gras?