Need help identifying algae

[TLM]

Need help to identifying the brown algae in the picture. It is growing quite fast. It is on few pieces of my live rock. And it is covering some of my green star polyps causes them not to open up. Should I just pull them off? What type of tang will eat them? Please help! Thanks!

[Matt]

It is hard to tell from the picture, but I think that's hydroids. If they are spreading, you might want to dose them with boiling water, vinegar, kalk, joe's juice, or something. They might sting you if you try to pick them off by hand. They'll likely cycle out, though. They don't tend to be stable.

[SeaHorse_Fanatic]

Hydroids. Not algae.

[christyf5]

Definitely hydroids, get out your hammer and chisel.

[TLM]

So what should I do? Pull them all out then?

[Delphinus]

If you can.. or cover them with epoxy, although I've heard they can just work their way around that. They can spread and they burrow deep into your rock so getting rid of them is not as easy as you'd think. They seem harmless but .. yeah, as you've noticed, they're not completely benign either.

[mark]

Get rid of them asap as they'll spread. Found kalk paste won't work and once established, you pretty much need to wreck the rock to get them out.

[TLM]

Some of them are covering my green star polyps. I tried to pull them out but it wasn't easy. Still got some left on the polyps. Is there anything I can try or do beside pull them out? Thanks again!

[fkshiu]

Hydroids are not easy to remove as they can come back no matter what you do to them. The only foolproof way I've found is the ol' hammer and chisel. I have also heard of people blowtorching them.

[Myka]

Sounds like you'll have to sacrifice some GSP. Hydroids can be a real pain in the butt to get rid of. I suggest removing any part of the rock that they are on, plus an inch around them.

[Matt]

Don't panic unless they're spreading rapidly. I've had a patch come and go without doing anything except fretting.