Harmless detrivore if Pacific, which it looks to be. The Caribbean variety is the one to avoid. Depends on whether you've gotten a lot of Caribbean specimens. I learned them first as horrid critters, when I lived in the south; now up north, with a different species, I've found them quite useful---two, this morning, nabbed a peppermint shrimp molt shell and tastefully disposed of it, before it hung about going to pieces.