The pic isn't real clear, but it appears to be cyano... The trapped bubbles are a tell-tell sign. Try to keep it brushed off the rocks and any corals it might be on, but be careful not to damage anything in the process (sometimes easier said than done). Do a search on this board for cyano and I'm sure you will find tons of tips on how to get rid of it. It's a common problem and one which I have had to battle in my own tanks from time to time.
Barney, the pic is a little too unclear to tell for sure,bvut looks like either cyano (is it green or red in color?) or dinoflagelates. Either way use a baster or piece of tubing to suck it up out of the tank and off of the rocks and SB or whatever it is on. Do not just brush it off and leave it in the tank. Removing it will get it out of the tank as well as all of the nutrients it has taken up.
I think its dinoflagellates, it doesnt have the consistancy of cyano its more fluffy like algae then a sheet like cyano, its also not colored like any cyano i've ever seen. I'll try and get a clearer picture tomorrow, the lights went out like 45 minutes ago. So scrub it with a toothbrush as i'm syphoning what scrubs off is a good way to get rid of dinoflagellates then?
If it's dinos you won't have to scrub, it will suck right up into the tube. You want to get it out of the tank, so be careful if you do scrub. Scrubbing it off intothe water column will only release all of the nutrioents back into the water column. Your going to have to do this 1-3 times a day till it clears up. It will cover and suffocate corals so stay on top of it.