Not a big problem. Although the sand in the back of the tank looks to be about 1" or less deep now. The front is at about 2-3". When I se too much new sand in the front. I just push it back down the holes - - gotta let him know I'm in charge. Yeah, right.
A lotta times, the holes he comes out of (and that the watchman watches) are covered the next day, and opended back up again. He just likes to push.
Anyway, if you do a pistol, make sure your rock is firmly planted on the bottom of the tank. Don't want the tunneling to cause an avalanche. Anyway, sounds like you want some thngs in your tank that the hawkfish might eat. Didja look it up yet? I'm being lazy.