I had been feeding salmon scraps to my duncans and acans. Because of this heavy feeding, I was starting to get some green hair algae showing up in my tanks. Within 2 days of putting 1 cup of GFO into my filter sock, I noticed my hair algae turning brown. I switched after 3 days and it is rapidly dying off. All this time, I have been feeding the salmon pieces every other day to help speed the growth of my corals.
I have been testing with the API test kits, and have yet to see any readable result. Both before adding and after adding the GFO.
Nothing concrete here, but I believe I got most of my phosphates out of my tanks in the first three days and now, I am able to feed heavily and still see an obvious impact on my hair algae.