"POP" "POP" "POP" I hear something going "POP" "POP" "POP" in my 20g cube! I wonder what it could be......

Maybe a mantis or more likely a candy cane pistol shrimp. My friend that I got the rock from said it could be a mantis but he did have a candy cane pistol shrimp go missing.
However what's really sad is that in my 230g tank with about 200 pounds of LR in it I can usually find my two-two and half inch bullseye pistol shrimp, my half an inch six line wrasse and tiny green clown goby, but in a 20g cube tank with 25 pounds of live rock in it I can't find the source of the "POP" "POP" "POP"
I also can't see were the small lose zoo frag I stuck on the rock last night disappeared to. I've seen it floating around several different times in the 230g, no problem (before I moved it to the 20g), but somehow in a 20g I can't see it anywhere WTF!
