When storing clams overnight you should store the clams overnight in the refrigerator in an open container and keep them covered with a moist cloth or paper towels.
When you store them in the refrigerator overnight in the open container the live clams will remain fresh for up to 3 days.
If you put the live clams in a sealed container then the clams will die so keep them in an open container in the refrigerator and they will remain fresh and alive for 3 days until you eat them.
I usually eat the clams within a few days so there's no need to worry about them dying or going bad.