I have a pistol in my 125g :) He wasn't a hitchhiker -- I bought him paired with a goby (who died, then paired with one of my firefish, who eventually died, too....but not because of the pistol), but he's still there, and hasn't bothered the fish. He does make clicking sounds. It sounds like crackling. It's how I know he's still alive lol But he's my li'l dude.