That's duckweed, probably brought in on the feet of some duck or Canada goose. It's not algae; rather, it's a simple plant. It eats algae and thrives on bodies of water with slow to no movement.
The only way to get rid of it is to remove it. I doubt it will actually grow much in your pool,
unless there is algae in there as well, which is likely to be present in the pool, brought in by the same feathered visitors.
What I would do is net up every little bit of the duckweed, then start a SLAM and increase the aeration/movement of the water at the surface. Thoroughly clean the pool of any organic matter. Clean or replace your filter cartridge (I was afraid you had a sand filter, which would have been a veritable smorgasbord for the duckweed!), and keep that FC at SLAM levels!
After you're clean again, you may want to watch closely for ducks or geese coming to your pool, and put on a spirited defense. Some people have had luck with something like this
Amazon.com: Aquascape 93000 Floating Alligator Decoy, 36 inches, Green: Gateway
www.amazon.com
Others wait and attack using a water spray from a hose. Search the site for "duck" and you'll get at least two recent threads.
Good luck!
