What is this?

[Dearth]

It is a bristle worm guaranteed if you have one you will have a lot more not seen vast majority are harmless and make a great CUC however never handle them bare handed as their bristles will give you anywhere from a mild jolt to full on pain.

2 species not generally accepted as being safe in your system are fire worms and enucid worms both are easily identifiable.

I personally am not a fan of bristle worms but I have way too many so I have learned to live with them