Glass Micro-cracking noise

[purge43]

I have no idea other then that to describe the noise Ive been hearing for months, but only noticed it as a constant occurance recently. it was set up as a fw tank for 20 years with only a few pounds of gravel. About a year ago i moved my reef in with 240+ lb rock on home depot egg crate supported front to back with 1/2 pvc spaced about 6 inches apart. The noise ive been hearing sounds like a low voltage spark. it really sounds like micro cracks in the glass. if Im tending to the tank over a course of a couple hours i would have heard it about twice. Im kinda a little worried, ive been hearing it alomst every day now. Does anyone know any physics about glass and what might be happening?

 

[purge43]

125 gal.

 

[Kataro]

is the tank set up w/ live rocks? if so.. maybe pistol shrimp or mantis shrimp.

 

[jimmyd01]

I would tend to think most likely the noise is coming from the egg crate under the rock, shifting, cracking.

 

[Leonardo_]

I also vote for pistol or mantis. I also thought it was the sound of sparks, it ended up to be a Pistol shrimp

Leonardo