Dealing with a predator in a reef

[freddy]

I'm new to canreef,your problem might be a crab,lost a sixline wrasse,clown@ a yellow watchman gobie,didn't know what it was,till I saw a crab about the size of a quarter eating him for lunch.Got rid of the crab,no problems.Didn't know I had a crab in my tank till then,hitchhiker on live rock I guess.

[trilinearmipmap]

If you're pretty sure it's a mantis or crab then if you don't have a lot of corals encrusted on your rock you could try dipping the rock, either a hypersalinity dip or a brief FW dip, especially if you have a good idea which rock the critter is hiding in.

I've had a clicking in the back of my tank since I set the tank up 4 or 5 years ago, never lost any fish to it and never saw any mantis. In the first year I trapped out 10 or 15 crabs but whatever is making the clicking never went into the trap.