What to do about diamond watchman goby...?

[Neuratox]

About 4 months ago I purchased a diamond watchman goby searching for a way to keep my sandbed clean while getting an interesting and pretty fish. It pretty quickly found a rock that it liked and built a tunnel under it, where it has lived ever since. The goby frequently comes out, explores the tank, sifts the sand, and eats well. It isn't bullied and isn't afraid of me. About a week ago I noticed that the mound outside of his/her cave entrance had grown more than usual... the following day it was burying corals and had gone from a 1" tall mound to 4" tall mound. I reach in every day now to try to spread the sand around, but its the same way by the time I come home from work the following day. I'm growing concerned for two reasons 1) the goby seems to favor sand in a particular area that I'm worried that, in time, will destabilize part of the rock work and cause a collapse (not sure if this will happen, but seems like a reasonable thing), 2) obviously I'm concerned about the health of the corals in this area as well.

Why is this behavior just starting to show? What purpose does this mound serve? Will this behavior stop soon? Can I discourage the behavior by trying to block the cave entrance and entice him/her to move to a new location (maybe bad idea)? Is it in the best interest of my corals and tank (rock collapse) to get rid of the goby and if so, are there any suggestions on how to do this easily? I do have an icecap fish trap.

 

[Cell]

The rock work should be against the bottom glass to prevent any toppling or crushing if livestock. The goby will go where it wants and the burying of corals is a well known issue with these obsessive sand sifters. Dont expect the behavior to change, just decide whether or not you can live with it or not.