Just thought I would chime in on the subject since I finally won my battle after nearly 4 months of fighting. I tried blackouts, peroxide, no water changes, siphoning every two days and on and on and on. Finally, I broke down and ordered Ultra Algae X. I followed all of the directions to the "T" and after 2 1/2 weeks, my tank never looked worse. Some people swear by the stuff, but I swear I won't put that in my tank again. What finally worked for me was the advice given by Julian Sprung. Cut the whites down to 4 hours a day and raise the alk up to 11-12 and keep it there. I also changed out my GFO every 3 to 4 days and in a couple of weeks it was completely gone. Not a strand to be found anywhere. Good luck with whatever treatment you decide to try as this plague is just the suck. Keep us posted!