I also like to change from 20% to even 50% of my water, depending on the tank.
I've had the red cyano
in all my tanks at the beginning, even with massive water changes. I've used chemical solutions though to fix the issue, I have no patience at all! I used red slime remover and the slime was gone overnight like a miracle. I also have not had any issues with the cyano
after the first initial outbreaks. If you choose to go with a chemical just be sure to read the instructions and follow them exactly. I had no ill results with my corals or fish while using it.