clicking sound in tank

[christyf5]

Soo...if one had a pistol or mantis shrimp in their tank it would make a clicking noise right? Kind of like a tapping sound against the glass? Is it fast or slow? Anyone have any experiences with this?

Reason is, something is in my tank making that sort of sound. Most times it is a single click, then sometimes followed by another a few seconds later. The clicks are never super close together, I'd say they'd be about a half a second apart or longer and theres only ever one or two. It happens more when the lights are off (ie. the morning) but sometimes when the lights are on as well, and of course never when I'm standing in front of the tank looking for the damned thing. I thought maybe it was something knocking around in the current but I can't find anything.

Am I just paranoid? Wait, don't answer that

*sigh* I never seem to just be able to sit around and enjoy my tank these days. Its always something