What is this green flat algae growth?

[Anastasia_usa]

Can anyone help me to identify this? It is growing only in one spot in my reef tank. (pictures attached).

It is green, flat, shaped almost like a fin. Brakes off in pieces quite easily but not easy to detach from the rock.

Is this algae? Normal or dangerous?

Thank you in advance!

 

[Stevarino]

Can you get another shot of it, possibly from a different angle?

If I had to guess I would probably go with Sargassum hystrix.

http://www.saltcorner.com/AquariumLibrary/browsespecies.php?CritterID=2072

 

[joshbrookkate]

Halimeda? If so, I read it's a slow grower.....

 

[anthonys51]

Halimeda? If so, I read it's a slow grower.....

Don't think it's halimeda algae. I agree with first guy but hard to tell from picture. B


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