Snapping noise - driving me nuts!!!!!

[Pazil]

OK heres the deal for the last 4 weeks I have been hearing a snapping noise coming from the tank. I have 1 for sure pistol shrimp that I purchaed about 3 months ago in there. I know his snapping and it is extremely loud. The snapping I am hearing is much quieter and coming from a different area of the tank.

I have not added any new rock to the tank in about 10 weeks. Is it possible that there could have been a mantis or pistol shrimp in there since I added this rock and have not seen him at all .... even once. I try to find the source of the snapping every night for at least an hour after lights out.... This and first thing in the morning is normally when it is most active.

Has anybody else ever heard of such a thing.... For something to be in there for this amount of time without being see.....My sanity is almost gone

Please help!!!!

Cheers
Stressed out Lawrence