It’s best to use mussels or any live shellfish on the same day that you purchase them. However, if you are not cooking them immediately once purchased, the best way to store them (for one day only) is on a bed of ice (with some ice on top as well) in a colander inside a bowl, uncovered. (See photo above for reference.) When ready to use, take them out of the refrigerator and clean them. You can return them to the refrigerator after cleaning without any ice while the tomato sauce is cooking.