Sorry no pics, just mysterious Clicking

Should this not work with just freshwater? I have had great success in scaring out bristle worms with scalding hot fresh water.

 

I saw the mantis shrimp last night at 4am, lol. def a Mr Mantis. im hoping that the coke bootle with pipe in it and a tasty treat inside should lure him out. Im gunna keep him too, in his own tank.... which will be tank no 3 (all good for power bills really)

 

Even tho this is an old post it seems. I can say now that i'm having a very similar problem. My tank has been setup for 5 months. the first four I never really heard much. Now im hearing exactly two clicks, very loud throughout the day. i've tried to dismiss it as mabye a random bit of water somehow hitting the light and popping or some miss in a mechanical device on the tank. But the recent loss of a Flame Angel and a Lawnmower blennie has got me scared. And now I know its not the lighting system because it is off and I just heard the sound as I am typing this message. really got me worried. let me know how you got the little dude out if you did.

 

I hear clicks from my tank too. I think I have a pistol shrimp, but as I've never seen it, the noise worries me a bit. Can be very loud.