My local grocery store gifts me clams that are open, and that can't be sold for human consumption. I freeze them then feed them to my tank. The Hippo in turn feeds it to everyone else. http://youtu.be/eLXYBs0sqeI
The fresh seafood place in town will NOT give or even sell me their un-consumables, but the grocery store will. Got to be sure to freeze them first, as it probably is kind of risky.
