Careful runaround. There can be a big difference between a sand bed looking good and one that is in good condition. Here is a link to Dr. Shimek's web site....
<a href="http://www.rshimek.com/reef/sediment.htm" target="_blank">http://www.rshimek.com/reef/sediment.htm</a>
I feel that crabs and shrimp are not good for the sand bed because of the creatures they will eat. You do not want a nice white sterile bed because it will not provide the denitrification we seek. The creatures are needed to slowly, but continuously turn the bed over. That is why the sand-sifting stars and burrowing gobies are not good for sand beds. Are they reef safe? Yes because they don't eat corals, but are they good for your reef in the long run. No.