Dark Maroon Algae

[newfishfiend08]

Hello,
I have a 65 gal tank with 70lbs of live rock that has been established for over a year and is doing wonderfully. The water specks are normal and have been so for over eight months now. Recently i've noticed a dark maroon algae covering my live rocks. I originally noticed it on the glass but just scraped it off. It does not cover the substrate nor does it look like its annoying the corals. I've had much lighter colonies of coraline algae on the rocks which has been covered. Is this just more coraline algae or something more sinister?

 

[salt life]

sounds like cyano, google it and see if it looks the same...
I think it is caused by not enough flow but correct me if I'm wrong.

 

[pezenfuego]

Usually cyano will be on the substrate more than the rocks

But if it comes up in a blanket and is slimy, then it's probably cyano. Look for pictures. Cyanobacteria