Found the article...I stand corrected, it did not say they are found on the sand bed, rather in all different parts of the rocky reef, I assume both in the rock work of the reef and potentially the sandy areas.
"Echinophyllia corals have learned to benefit from the high level of sediment that settles down on them from the current. They are able to use sediment as a source of nutrition by selectively extracting organic matter and transferring it directly to their tissue. Once the sediments are depleted of nutritional value, the corals use their natural sediment-rejecting abilities with mucous to clean their surface for the next batch"
pg. 50 CORAL January-February 2011
This is exactly what I see with my larger chalices on the sand bed, they will be 75% covered with sand and within a few hours only 20% covered, then an hour later completely sand free

. I doubt my chalices are getting a whole lot of nutrition from the sand deposited on them by my leopard wrasse but they are exhibiting the ability to remove the sand with their mucous

.