Digging Wrasse

You're sure it's a wrasse?  Not an engineer goby, or watchman goby?  I figured I'd chime in and then maybe some more experienced people will answer.  It doesn't seem to me like it would be bad to have him digging, at least from a chemical standpoint.  Hopefully he's creating new places for amphipods, copepods, etc.  Making your substrate a more diverse environment.  Hopefully.  What I would worry about is your rock falling over.  Did you put the sand in first, and then set the rock on top?  Or the rock in first, and then substrate? If you went the first route, I'd think your rock could topple.  We did a combination of the two, and our watchman goby builds some tall pyramids of substrate.  So far, so good.

Can you point us to a pic or description? It is very unusual for a wrasse to be constantly digging in the substrate.

I'll bet that it is finding food there. It is definitely damaging your filtration.

What else do you have in the tank? There may be a need to take some quick action to remove the wrasse or feed it. Wrasses enjoy all the little bugs that live in a mature reef. If the reef isn't old enough or is populated by carnivores like Wrasses, Psuedochromis, Royal Gramma, Basselets, and Damsels(includes clownfish) it may eventually crash with an algae bloom, sometimes preceded by massive fish death.

Suggested reading is the article by some crazy guy in the June 2001 issue of the Sea Star Online (blue button to the left) titled Herbivores vs. Carnivores (Algae control and fish defined).

Is he sleeping in a different spot each night?  If it's the same spot I wouldn't worry too much.  My father-in-law has a yellow wrasse that sleeps in the exact same spot every night.  I like watching him dive into the sand.

Wrasse bury themselves every night.  I don't think it will hurt your filtration, it is just more reason to have a very large deep sand bed, so that the disturbed areas are of minimal size. 

Adam