Pistol Shrimp gone feral?

[gobytron]

Some pistols are more predatory than others.
you would need a VERY strong pistol shrimp to break through snail or crab shells...

I had a large peacock mantis that couldnt get through a shell easily.

You should check to make sure they are not molts.
also make sure you have extra shells as a crab that outgrown his home who cant find a new,, bigger one will perish.