Its funny because some animals actually have SANDSIFTING in front of them like sandsifting star or the sandsifting goby. but i like the sandsifting gobies because its fun to watch them actively pick up the sand and sift it
Nassarius snails are your best bet. I'd pass on the sandsifting star if I were you -- it will quickly starve to death in your tank. There are types of reef safe sea cucumbers too.