Im not gonna lie hes real cool looking.
If he was for sure good then id love to keep him.

But then again if hes going to spawn more and become a problem then id rather get rid of him now.

I think id rather save what I have then risk losing it all in the future.

I was reading that I could do a fresh water dip of the rock. Problem is that the rock I last saw him on was the one with the 2 Mushrooms.
Would it hurt the mushrooms?

This way would apparently make him run out then I can take a picture of him.

If that doesnt work then how can I just kill him...

Doing a fresh water dip (don't use cold water!) won't really hurt your mushrooms. They're pretty resilient. A fresh water dip, preferably with Lugol's or Salifert, usually kills the nudi's or atleast makes them fall off the rock. Otherwise, you gotta doing it manually with your turkey baster or tweezers.

Quick Update.
I havent taken the worm out yet but I have identified it as a Bristle worm!

I have around 5 noticeably different species of bristle worms in my system (apparently thousands exist). The only problem they have ever caused me is when I touch them with my bare hands I receive some irritation for a day. Other than that most of them are harmless and actually beneficial to keep. Plus once they establish themselves in your tank they are pretty much impossible to get rid of.

Not trying to hijack. But how big do most people let the bristle worms get before they are removed? I've got some that are 10-12" long, but when I catch them they shrink down to 2" with more girth.

:idea: Update:
Alright so I fresh water dipped the rock I saw him on. He was on that rock to because I saw him pop out.

Tons of red brittle star fish and black ones and some little worm thing.
But no bristle worm. I let the rock sit in the water a bit and ran some on it too trying to rush him out.

Few days later.
5minutes ago I just saw him coming out the SAME rock. AND HES HUGE!
Hes like 5" LONG NOW.
Hes not eating my frogspawn or my mushrooms. Maybe hes eating the Halimeda Plant in there...

I shot him with PURE concentrated salt water. Now im waiting to see if he survived...