Pretty sure I know what this is.

[Sideshowbob]

Pistol shrimp right?
It's definitly pretty reactive and came in on a frag I picked up from one my lfs's.
Question is I've heard they can Crack glass, my take is acrylic Has anyone ever run into problems with these guys?

 

[Lionfish Lair]

Yup it's a pistol. No, he can't break glass. I would pop him right on in the tank. I had one for years I never saw, but only heard.

 

[Sideshowbob]

Appreciate the confirmation.

 

[Lionfish Lair]

Mine sounded like a glass heater hitting off the side of the glass tank. He would start to snap a lot during feeding time. I enjoyed knowing he was in there.

 

[Weeble10]

I have pistols in two of my tanks and they are a fun addition to your reef!

No worries about cracking glass, but they dig and burrow in the sand under your Aquascape so make sure your structure is stable.