I have been hearing clicking sounds ALOT lately in my tank. So I either have a Mantis or a pistol. Now I havnt had any empty shells from my hermits, or snails anywhere. Except the 2 empty snail shells the hermits took out in the very front of the tank..no where near the clicking. So its in the back of the tank and I have been trying to pinpoint it forever now. it seems to click in a rapid fire way..alot like my old pistol shrimps use to when something got near it. Also it usually lets off a burst of clicks when i turn the lights out as well. Kinda making me thing its a pistol since a mantis usually doesnt just click for no reason at all. I think it might be in this one rock that isnt to big and I could pull out for a quick FW dip to see if it comes out. I really hope its not a mantis.