Is this what's killing my snails and hermit crabs?

[tgurske]

I spotted this little guy tonight. No idea what it is or where it came from. Any idea what it is and if it could be what's killing my cleanup crew?

 

[griss]

Hard to tell from the pic, looks like it might be a gorilla crab. If so, it might harm snails but, likely IME won’t bother hermits.

Where did you source your live rock? With both hermits and snails dying, I suspect a mantis shrimp.

 

[tgurske]

Thank you!!!

 

[Sugar Magnolia]

I agree with a type of hitchhiker crab. Gorilla likely. They are opportunistic feeders and will eat what is readily available, including hermits. I had one that I couldn't catch for months. It had grown to the size of a 50 cent piece. It ate countless snails and hermits but it had to go when I caught it eating my Randall's goby.