Had everything in the tank for a while, adopted some fish/crabs and rock from a friend a couple weeks ago, I don't remember them saying anything about clicking. Heard a double clicking noise like someone turning on/off a light three times.. pulled out the flashlight and didn't see anything, fish alive and fine. Set a trap and.. caught a hermit crab. Emptied out the rock and checked every piece & the sand.. and didn't see anything unusual, although I do have a very clean tank now. Fred sometimes makes noises with the heater, am I okay in relaxing? I'll keep an eye out, but I think that covers all the techniques from previous threads.