[Dearth]

As Mindy said sea cucumbers are great sand sifters I have tiger tails in my tank and they do a great job and can reproduce asexually I e gone from as little as one in my tank to as many as eight they ebb and flow with food demand

Snails certain species are sand burrowers and do a good job of turning over the sand however it should be noted if you have hermit crabs you will lose a certain amount of snails to the hermits as they are buggers

Sand sifting gobies are also great at sifting sand but come with a caveat all your rockwork should lay on the bottom of the tank as the gobies are known to make caves under rock and can collapse rocks on themselves