I need help identifying these strange things

[desagon]

I found these on a rock near my green palys. I never really thought much when I first noticed them about a couple of months ago, but now I’m wondering what they are and if they’re good or bad. To start, they’re very small and instead of growing like I thought they would, they just multiply. And by small, I mean like 2-3mm across. Also, they have long tentacles and appear to be fuzzy when viewed from afar just because of their size and the amount of them in a concentrated area.
I tried to take the best picture and describe these the best I could. Any help is appreciated.

 

[andrewey]

Are you able to take a picture with your blue off and just the white light (if that's possible).

 

[C. Eymann]

Pretty blurry, but unfortunately I think those are colonial hydroids

 

[AcroNem]

I agree, hydroids

 

[desagon]

Here’s another pic. Colonial hybroid? I did a google search and I couldn’t find anything about them. What are they?

 

[andrewey]

If hydroids, they are similar to tiny jellyfish. Very common in new tanks, most go away on their own in a matter of months. A real problem with seahorses/pipefish, otherwise not a real concern for most reefrs. Can eliminate if you want to or reduce numbers with reduced feeding/mechanical filtration, but usually doing nothing will reduce their numbers/eliminate them.

 

[desagon]

Thank you! That was very helpful!