Is this a fully cycled tank in which you changed out the substrate to create a DSB? The sand will eventually settle. If it sticks to the front glass you may want to wipe that off with a paper towel. If it settles on rocks or corals, use a turkey baster to blow it carefully off. If the tank had already been cycled, it is safe to return snails and other creatures to the cloudy water. If it is still the extreme "milk vat" cloudiness you could hold off another day or so. It sounded like you were already past that stage.