I have a 28g nano tank, the only inhabitants (other than snails) are a lawnmower blenny and a clownfish. I got a pistol shrimp and I am intending on getting a watchman goby and that will be it for stocking.... anyway it was about 3 weeks ago and I have yet to see the pistol shrimp since the first day! I have a big pile of branch live rock so it is pretty easy for him to hide. But sand is appearing in strange places and pits are being dug so he must be coming out sometime...I'm sure nobody else is doing this digging, but even if I turn the lights on suddenly at night I never see him! Will he ever decide to come out so I can see him? Also do they generally make that snapping noise occasionally or is it only when attacked? I've heard some noises coming from the tank that sounds like it during the day... at first I thought it was a glass thermometer that I had floating in the tank bumping up against the glass... but then I realized that I don't have that thermometer in there anymore...?