How do I get rid of this little bastard? I put in some new rock, and it came with a mantis shrimp that ate my fish and is recking house on my hermet crabs.
Clear pop bottle. Cut off the top 1/3, invert it, and attach it to form a trap. Bait the trap with some sand (weight), and meaty seafood. Position near the bottom of the tank just before lights out.
You'll have to be patient. You'll probably catch lots of other critters first.
Are there corals in the tank? A harlequin tusk may eat smaller mantis. But unfortunately, the best way is to find the rock it's in and remove it. It's really hard to do (I know from personal experience ).