2020-6-16 · Click to see full answer. Accordingly, how do you crush oyster shells? First, buy a bag of oyster shells from a feed store, then bake them at 250°F for 10 minutes to kill off any bacteria. Next, stuff the shells into an old sack, pillowcase, or feed bag and use a hammer to smash them into bite-size pieces no larger than your fingernail.
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