What are these critters in my tank?

[Elise_]

Hey guys,
I have been having some trouble with my tank and my corals seem to be going backwards, even my soft corals - mushrooms and zoas. But particularly my Lps. My euphyllia both bailed out and my Acans don’t look the best.

I got home late the other night and noticed a bunch of these long white feathery looking strands coming from everywhere in the tank and they seemed to retract when I shone a light on them.

Any idea what these are? Is it a problem and are these bothering my corals or does it indicate an issue with the tank otherwise?
I’m so confused!

Edit - also managed to get a video clip uploaded.
Video

 

[Elise_]

For some reason the video will not play, so I have snapped a new photo

 

[damsels are not mean]

Never seen anything like that before so I'm following. My best guess is vermetid snails but those don't tend to have feathery strings like that. Do they only come out when lights are out or during the day as well?

 

[itselenababe]

If you go to the common hitchhikers sticky thread it’s on there. I forget what it called, some kind of hydroid

 

[itselenababe]

Under the hitchhiker I’d forum^

 

[Elise_]

Thanks all, I had no idea that thread even existed - pardon my ignorance!
Now to try and work out how to get rid of them, they only seem to come out at night so I imagine trying to find them to kill them is going to be tough. Hopefully this doesn't mean I need to pull the rocks and start over

 

[ying yang]

Digitate hydroid

 

[YOYOYOReefer]

They are called Digitate Hydroids
hydrogen peroxide will kill them
lynx nudibranch is what i would try if they are in hard to get to spots.

 

[ying yang]

Digitate hydroids spreading. What to do?

I've got a Fluval edge 6g nano that's been up and running about 5 weeks now. No fish, just CUC and random hitchhikers. I noticed the first couple of d.hydroids a couple weeks ago isolated to one rock. They have since spread to most of the other rocks. Not infestation levels yet, but a good 6-7...

www.reef2reef.com

Few suggested ways in this thread also,never had them so no first hand experience