Unknown mass spreading on zoas

[critncarter]

I am relatively new to the reef tank hobby and have a problem with some zoanthid corals. There is a solid brown/purple mass spreading over the coral and covering polyps, it was relatively slow spreading to begin with but has started to spread faster, covering more and more of the coral. I have tried to search for what it is and how to stop it but have not seen nothing like this so I was wondering if anyone could give a diagnosis from the photo attached.
Thanks.

 

[Reefer40b]

Coraline. Urchins eat it

 

[critncarter]

Coraline. Urchins eat it

Hi,
Sorry, I think you’re looking at the wrong part of the photo, I meant the dark brown mass that’s actually on top of the coral. It is rock solid and I’m unable to scrape or take it off. I’ll send another photo that may be clearer. Unless this is coraline but I think you were looking at the light purple rather than the more brown section.
Thanks.

 

[Krixic]

Hi,
Sorry, I think you’re looking at the wrong part of the photo, I meant the dark brown mass that’s actually on top of the coral. It is rock solid and I’m unable to scrape or take it off. I’ll send another photo that may be clearer. Unless this is coraline but I think you were looking at the light purple rather than the more brown section.
Thanks.

Not super sure but did some research and looks like it could possibly be Lobophora. Is it growing on your Zoas? And does it fan out at all like a moni would? Although I've see some that dont fan out and stay flat like coraline would.

 

[Reverend Turtle]

It's got to be some kind of macro algae. Unless it's fuzzy, then I guess it could be an encrusting coral.

 

[Tankkeepers]

Is it hairy and Fast growing

 

[Tankkeepers]

Like velvet if so it could be turf algae

 

[Tankkeepers]

If not id agree about it being Lobophora looks very very similar

 

[Anchor]

I am going to go with a red brush algae. I have had some and it is near impossible to scrape off a rock.. Urchins will eat it but it isnt a favorite food or certain. I to have had it grow over Zoas and GSP as well.

 

[Reefer40b]

Oh I see yes I have had that before, turf stuff to scrap off and grows over everything eventually you will win the battle.

 

[Anchor]

One place I find it showing up a LOT is on Trochus snail shells.. and then spreads around the tank.. I try to scrub the shell before putting it in the tank and even treating the shells with peroxide.. but cant get it tall and one thing I found with using peroxide is that is may kill the current growth but does not get the roots.. if algae even has roots.