What's this worm? ID Please

[SHNICI]

I saw that one on one rock, it was coming out after I take off the lights, and it was feeding on live creatures, like a copepods, brine shrimps, amphipods etc ... Wasn't easy to catch him, but at the end it's in separate box out of the tank xD
Can you let me know is it bad (or only eat what I already saw), if it's going to grow too big, probably can pray and other invertebrates in the tank ?
At the moment it's over 6cm / 2 inches :

All the Images: -> https://photos.app.goo.gl/214LC62X1C6dFkQP6 <-

Regards: SHNICI - Georgi

 

[Crabs McJones]

Bobbit worm, remove asap

 

[Holy_makerel]

Looks like it might be a bobbit worm. Some folks love em and you might find someone to take it

 

[SHNICI]

Bobbit worm, remove asap

Yea, I left it for a while in the tank observing it under red LED light (he don't see the red light probably), and it took me over 40-50 minutes to stay over the peace of rock with the tweezers like frozen, to get the perfect moment, very fast creature xD

Looks like it might be a bobbit worm. Some folks love em and you might find someone to take it

I'm in UK, if some one is interested in...... it's free to write me and I'll post it

Regards: SHNICI - Georgi

 

[Eastlake]

Yep, that there is a baby sea monster (Eunicid worm). You could set up a separate tank for it to amaze the kids, frighten the in-laws, and spend the rest of your evenings sleeplessly wondering when it will escape its confines and come for you next. In all seriousness though, most of them are predatory in some respect and if you witnessed it eating various amphipods and copepods then it likely will grow up to eat anything that it can get its jaws on. You're lucky you managed to get it out of there while it was still small, or that it was gracious enough to reveal itself to you while it's still small.

 

[Lovemyreef2015]

Looks like a Perinereis cultrifera (ragworm)

 

[SHNICI]

Looks like a Perinereis cultrifera (ragworm)

looking on the web, it look like the one which you say. have to read about...., how bad this one is and how big it grow and how it reproduce and it's mature, to be able to decide is it possibility there to be more in the tank eggs/ larvae etc ......