I had cyano really bad for awhile. I did 2 things and it has pretty much wiped it all out. I added 2 units of Chemipure to my 75g. Which I'm debating whether it helped or not. The biggest thing that I saw make a difference was, and I know it sounds strange, but I started emptying my skimmer cup every day or every other day. Once I started doing that consistently, I saw huge improvements.