Deep sand bed help

[Shakeel]

Ok I have a 4+ inch sand bed in my six footer 150 and everything was ok til I picked up an Royal Grammer.
But I was content because he just dug a nice little hole under a piece of live rock.
Ok here is the problem I have a clown fish named kujo (bites any hand that enters the tank)he have become buds with Ninja (royal Grammer)and thinks that he needs a bigger hole under the rock and everyday really clears it out for him.
What can I do to stop this diggin cause kujo is really disturbing my dsb?

 

[NanaReefer]

Not a thing :(

 

[Downbeach]

Very common for clowns, and any damsel type to dig. You could try getting a BTA for it to host in your rock work, but that's another issue.