Help with Black coating on live rock?

[Reefmongrel]

On a few of my live rocks in my 90g , a black coating with some bubbles has formed. Fish and corals are healthy. Some green filamentous algae grows on glass over a week.
Have a 30 g fuge with macro algae - harvest every couple weeks. This black coating appears to have wiped out anything else on that portion of the rock.
Lighting is MH and actinincs - on about 9 hours daily.

I used some maracyn a few weeks ago in the fuge to remove some red cyano and I wonder if this has had some competitive effect with good bacteria.

Anyone have ideas of what it is and how to remove?

Reefmongrel

 

[brownchinchilla]

Any chance of putting up some pics?

 

[Reefmongrel]

I think I posted a picture in my gallery - click there and open pic.
Reefmongrel

 

[jjmcat]

Maybe a new stran of cyano?I has a bad outbreak of neon green cyano in my tank.Hard to get rid of.I had to use a product called red slime remover to get rid of it.Just be careful what you do as I lost 2 acros.

 

[Reefmongrel]

Thanks for the reply.