If you have hair Algae or Turf Algae or like stated your Phos. is on the high side or rising GFO will help. Rowa does work well and some say it is the best, but it does leach Iron which can be good and be bad. It will not do much for Cyano, if it is true Cyano. You can test by put some Peroxide in a small container and remove some of the Red Slime and add it to the Peroxide. If the everything turns red it is Cyano and I believe if it turns Green or anything either then Red it is Spirulina. Cyano is caused by detritus build up on rocks and sand bed, it covers it and uses the detritus to feed on, it is a Bacteria and is called so Cyano-Bacteria. I just dealt with some myself. I found that ChemiClean worked out to be the best and easiest. 1 small scoop per 10 gal. The trick is to try and determine your as close as possible your true water volume, as you do not want to over dose the tank. What I did was I have a 110 gal ( some say 112 gal ) so account for rock sand and sump I figured around the 100 gal mark, so I played safe and added 8 scoops and after first day everything was fine and added the other two. Shut skimmer off and let it do its thing. I did not really see much until the third day, that is when I seen the biggest improvement. Left it one more day and did water change and added carbon and all is good. Some Corals will show some signs of stress but I did not see anything major. If you chews to use it just follow the instructions and not just part of them.
