I fed some shrimp tails this morning and the tails were gone in minutes. The other day we had Alaskan king crab and had a considerable amount of shell debris after that dinner. I put the crab shells in the the outdoor grill on a cookie sheet and baked the shells until dry. The next day I put them in a plastic bag and crushed all the shells and threw them in with the chickens. That night the shells were all gone and the birds are all still doing well.