The only place I had to set up my one tank (20 long) gets a fair amount of ambient sunlight. The plants are just starting to take off, but so is the blue green algae on all of my glass. There are no fish in the tank yet. I've read good things and bad about duckweed, and I'm wondering if it would make sense in my situation.
I would NOT do regular duckweed unless your prepared to fight it from now on.
Perhaps in most regular tanks it might not be hard to remove all of it.
Giant duckweed is just a slight bit smaller than Salvinia and is easy to control.
I don't think any of these will work on BGA. It's actually a bacteria, not an algae. http://www.guitarfish.org/algae
If you use the last cure on the list and then address any problems listed above it, the BGA may not come back.