I know for a fact that GDA is light dependant. When I do a brown out, it doesn't grow at all. That said, a 3 day brown-out will only slow it's growth. The GDA will quickly grow back as soon as you turn the light back on for more than 5 hours (on day 4 or 5).
So a way to inhibit regrowth after a thorough cleaning of the tank is to limit the light as Tom suggest to no more than 5 hours per day.
Frequent water changes do help keep GDA in check. If you do a >50% water change with cleaning the glass every 3 days, this helps. The GDA might come back as soon as you return to the 1 x per week WC.
I think this GDA is seasonal as Tom suggested.
No problems usually during the winter months. Full out blooms during the summer. Thsi was true for my Mini-M, too. I'll have to check when I tore that tank down. I was tired of cleaning every 3 days just to have the GDA come back. If we conclude that this is seasonal, I'll probably stick this out till next winter to see if GDA is dormant during the winter. That would provide us with a "light at the end of the tunnel" and a much needed rest from water changes...lol
I think I've found our GDA friend in other places, too. Although I haven't ID'd this algae as GDA under a scope, this algae is very similar.
Here it is in the planting soil. It's not BGA (doesn't smell bad like BGA). The algae is thick, bright green, and acts just like the GDA that grows beneath the aquasoil in my tank:
Here it is again around the base of a potted plant:
Here it is in a house plant vase (indoor plant submerged):
Assuming this is the same algae (big assumption), the only two things that are in common with my fish tank is the water and the air.
I think we can rule out water, unless San Francisco does something different than SAC. Tom doesn't have GDA and I do (same water source? Hetch Hetchy?
Are the water additives the same year around, or do they change during the summer months?
The other, more reasonable assumption would be the air...spores. We've been doing a lot more watering during the summer. Our windows are always open. Temps are higher (for the most part).
Anyway, this GDA seems very prolific.
Good thing it stays mainly on the glass and hardscape areas with some substrate involvement. It's easy to clean, just labor intensive.
Increased phosphates didn't help my situation. I went from a pinch to a dash last week.
AlsoI clean my CO2 diffusers one a week in bleach. Just broke my ADA and replaced it. I also move its location to directly across from the lily pipe outflow. Maybe better circulation of co2 will have an effect.
Nevertheless, I'll plan to do a water change every 3 days to keep this in check.