Hydroids? What do you think

[jnava19]

Hello!
I found this things today when closely watching a rock, I think I saw them before as tiny green circles. One or two. Today saw them bigger and with hair? (Not sure how to describe it)

From what I found looks like Hydroids, but could not find a lot of info. What do you think? Good? Bad? They are only in those spots for now.

Thanks in advance for any info.

 

[KJ]

Colonial hydroids.

 

[jnava19]

Colonial hydroids.

Thanks! I looked for it and found this other thread here https://www.reef2reef.com/threads/colonial-hydroids.441987/
I would not like to wait to see if they grow though, but don't want to go with any chemical, if I glue a rock on top of them will that work? (do they need light?)