When I added my japanese snapping shrimp it immediately went to town digging out all the sand from under my rocks (luckily I had the foresight to put them all the way at the bottom of the tank, but I was worried at first because I couldn't remember if I did... Anyways, so the shrimp has removed all the sand it seems from inside the rocks, piled it up on the entrances but now just hangs out perched up in the rocks, doesn't dig any more. Moves between two spots but always up in the rock crevices. My only concern is he's created a sort of gauntlet between my nem and I hear him snapping occasionally (I assume) as fish swim by; have yet to witness a live fire. What gives? I thought these shrimp dug a tunnel and maintained it... there's at least 2-3 inches of sand to play in...