Try this home-made trap, and put it in after lights out:
You could add a puffer, moray, or trigger, that could work too...........
Oh, and next time you add LR
to the tank, try this, I found a couple that never got to my tank.
When the rock is cured and ready to go in, mix up a batch of saltwater in a 5 gallon bucket that is SUPER salty, like off the hydro chart salty.
Dip the rock in the bucket, real quick, and jump back because if there is a mantis up in the rock, he most likely will bolt from it and land in your lap at this point.
Rinse and repeat......