I fought cyano for a year when a giant old engineer goby died way back in my reef. Water exchanges helped a little. But I am not a fan of adding antibiotics and I thought my ATS would do the job, but P04 stayed up at .4ppm. I hate GFO, for several reasons I have described in lengthy detail, but I decided to try Rowaphos for the first time. Good news and bad news. I brought my P04 down to .08ppm, destroyed the cyano over about 60 days, but it also killed a couple of my favorite corals as the levels fluctuated. Just another example of how stability is the main factor in reef keeping. I keep Rowaphos tumbling in a reactor, it doesn't clump like GFO does and my levels are now once again stable. You have to eliminate the nutrient source to get rid of cyano for good.
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