What are these little white things?

[Phyrenite]

So I woke up this morning and found my Alveopora not extending and had these little white worm looking things near it. I dipped it and used a soft toothbrush to brush them off my live rock. (I didn't take a picture then)

Tonight i found some more though, what are they? They dont seem to be moving, at least not very quickly, but are they dangerous to my tank? Currently they are only in this spot.

Thanks ahead of time for the help!

 

[OrchidMiss]

So I woke up this morning and found my Alveopora not extending and had these little white worm looking things near it. I dipped it and used a soft toothbrush to brush them off my live rock. (I didn't take a picture then)

Tonight i found some more though, what are they? They dont seem to be moving, at least not very quickly, but are they dangerous to my tank? Currently they are only in this spot.

Thanks ahead of time for the help!

They look like thin tube worms to me. They're harmless filter feeders.