So lately I've been battling high nitrates and did a 20% water change then 10% every other day for about 2 weeks. My water is clearing up and levels are returning to normal. I've also had a problem with sunlight hitting my tank through a window that I just now covered. I also built a counter current protein skimmer that is now producing dark green skimmate. I'm reducing feedings per day down to only twice a day. I've still got this gunk on the rock that was hit by direct sunlight for the majority of the day. Any ideas what might help fully eliminate this?