Bad news. This stuff will make you appreciate Red Slime (Ocillatoria); which is much easier to eliminate. In all the years I've been keeping saltwater this green cyanobacteria is the most invasive of any pest I've ever encountered. It will quickly cover every inch of your tank. Even in a tank that's never had algae problems. The best way to deal with it is to get phosphates and nitrates (nutrients) to zero. I've found out that running GFO and carbon really helps. Went lights out for three days and it came back.
Siphon it out every day in the middle of the light cycle before it encysts. I did 5 gallon siphons every day for two weeks before I got a handle on it. Sometimes I did 10 gallon water changes because 5 gal wasn't enough to get it.
If you don't get very aggressive with it, I'd predict you'll be tearing down your tank. I cannot stress that enough - it is the worst plague I have ever encountered.