Nassarius snail is a good choice... Conch too...
As they will burrow themselves in the sand in the day and that will loosen up the sand and prevent solidification of the sand..
Brittlestars, Heart Urchin... If you dun mind seeing a big long thing on your sand bed, sea cukes is a good choice too...
If for fishes, Not much to recommend, other than the difficult to keep two spot goby.. The other sand shifting goby are really terror to reefer as they tend to bomb the corals on/nearby the sandbed...