As others have said there are a variety of snails which do the job well. Best of them all would be sleeper gobies imo
. I have a gold headed sleeper goby, a sand sifting star fish, and about 20+ snails. My sand had a lot of small shells in it apparently, and they have been digging them up ever since I put them in there. I have sucked out a lot of them (not full shells) and the next day there are so many more again. The gobies do a well job of stiring up your sand when you first put them in. And when they claim their home under a rock, they will thouroughly clean that area. My goby is living under a rock on the right side of my tank. The sand he has tossed out the back, looks cleaner than ever.