Terryz, you are right. There is absolutely no need for any critters on top, probably a shrimp but with enough flow, there would not be a need.....
There is no need to worry abt caking of sand in the DSB as the critters living in the sand [fauna, tiny tube worms, etc etc] will handle them.
A gd read on sand bed.
http://reefkeeping.com/issues/2003-06/rs/feature/index.php
btw, can link other forums here?