My scrubber is stripping all nutrients from the water and actually working to well. I reduced the lighting period from 14 hours to 12 hours and a week later I am still not really seeing nitrates come up. I just reduced lighting period again to 10 hours and will test again in a week. What would be the minimum lighting period before I need to find other ways to get nutrients up? The intensity is at the 3:00 position The scrubber is almost 4 years old.