My tank has been established for 2+ years and for about a month now, I have been battling red algae. My lights are on for 9 hours, I feed twice daily, do 5-10 gal weekly water changes with ro/di water. My lights are new. I tested my water levels and my nitrite, nitrate, ammonia, phosphate are all at 0. I siphon most of it that covers that rocks and sand bed. Tank is not near windows. I have to admit, there are detritus materials underneath the red algae, how do I get them out? Any advice? I was told that I can't mix through the sand bed when I am doing water changes.