First time iv come across hitch hikers and I believe they are bristle worms should I be afraid they will

[Vg1]

First time iv come across hitch hikers and I believe they are bristle worms should I be afraid they will multiple?

 

[KJ]

Brittle starfish good CUC.

 

[Mikedawg]

A lot of us hope and pray to find some in our tanks! Probably want to check on one near the bottom; sure you know they can regenerate legs as seen on rock.