I have a 35 RSM tank that has been up and running for over 5 years. The tank is doing very well. All of the parameters are within Norm. The only problem I have is the sand bed continues to accumulate algae. I do water changes every week, clean the sand bed and a week later it back. Doesn't really get worse or better. This is only effecting the sandbed. One idea I contemplated was replacing the sand with fresh. I might add I have a second 35 RSM and it not have the same problems. Had anyone had a similar problem or can make a recommendation. I would prefer a nature solution not chemical.