Hard to say, this looks like a newer tank? Are you adding any carbon? If this is a new tank it may just be diatoms with a smattering of cyano.
Have you tried increasing flow, blowing the unknown off the rocks with a turkey baster?
Fairly new tank. Only couple months old. It dosent really blow off when I point the power head at it. I'll try upping the flow. Maybe can bet better pics for ID
It did blow off when I pointed the power head at it. Blew off as much as I could then did a water change. I also did recently start using ecobak ez in a reactor. So maybe once that gets colonized the algae will go away.