Request ID of worm in sump tank

[AudioGoose45]

So this weekend I bought some macroalgae from a LFS. Couple of days later, we spotted this guy (fug light off, looking at it with a phone flashlight) crawling through the macroalgae. He's a worm thingamabobber with spikey thingies. Any idea of what he is and does he stay or does he go?

 

[Mikedawg]

Looks like common bristle worm to me; nothing to be concerned about and many like them as part of cuc. Good find

 

[AudioGoose45]

Looks like common bristle worm to me; nothing to be concerned about and many like them as part of cuc. Good find

Thank you.