I don't rate the blanket trick at all. Algae is pretty sturdy, and it's going to take more than 2 or 3 daysto get rid of it. To do an effective job look on reefcentral.com at the threads on 'cooking 'live rock', which involves keeping it in the dark for 6 weeks at a time.
You're going to take a damn long time to gt rid of that by just limiting nutrient as well, plus you have so much it's probably choking water flow to the live rock and limiting that's filtration abilities. I would I'm afraid be looking at manual removal, which may well involve , at a water change, getting the live rock out of the tank to toothbrush the stuff off.
Not pretty, not easy but you have a lot of algae there and you'll be looking for some extreme measures. Or get the nutrient under control, get a good skimmer and get something that will eat it, and do it fast like a blenny.