Mantis or Pistol Shrimp?

[Oscar]

Well I still hear the occasional clicking but other than a molts a few months ago no sign of a pistol shrimp. I removed a hitchhiker crab a few weeks ago.

I do have one suspicious pile of sand in one corner of my tank that has been there a few months. I have changed the water flow thinkig it might be a "dead spot" but it is still there. Looks like an ant hill with no real opening.

Before I add a shrimp goby to the tank I would like to confirm I have a pistol shrimp in residence. Will dismantling the ant hill tell me anything
? Any other tricks?