The "audio taper" is a specific type of potentiometer used in audio equipment. It has a much more linear resistance chart (others are not). But what matters here is that this potentiometer works opposite of logic - turning it clockwise actually decreases the intensity. When I put a unit together, the 12 o'clock position is always 100%, and that is with the knob turned all the way counter-clockwise. At least, it should be. Unless I was really off my game that day, but I'm pretty adament about that knob position So if you turn it all the way left/counterclockwise, it should be maximum intensity. Turn all the way right/clockwise and you should be at 11 o'clock and that would be about 10% intensity. It's rare that you would ever need to run the LEDs at anything less than about 40-50%, which is the 6 o'clock position. In some cases, it's appropriate. I plan on going into depth about this eventually. So for anyone running the scrubber at the initial 6 o'clock position for 9 hours/day, if that's working for you, great! But after you get initial growth, you typically want to bump up the intensity to 4 or 5 o'clock as soon as you have growth that covers most of the screen (usually this is a couple of weeks but it depends on the individual system) Then after you are at 4 o'clock for at least one "harvest" you can add hours, go to 10-12. After that, it's dependent on your system. I recommend alternating increasing intensity and duration; so you might do something like: Start at 6 o'clock for 9 hrs/day After 1-2 weeks (and growth covering screen) go to 4 o'clock +1 week, duration to 12 hours +1 week, intensity to 3 o'clock +2 harvest cycles, duration to 14-16 hours (harvest cycle is as needed, 7-14 days, 2 cycles just to be sure that the growth does not revert) +1 harvest cycle, intensity to 2 o'clock (only if nutrients are available - this means a large tank with measurable nutrients or a small tank with elevated, or any tank with an algae issue) At this point you have to start watching the growth to make sure the intensity isn't too much. You can generally increase duration pretty long at a given intensity level. It's all about balance. Intensity relies on continuous (instantaneous) nutrient delivery to be able to sustain that level of photosynthetic production, so rapidly increasing it might mean you shoot past the balance point. If you're at a stable point and you increase the duration, that's not going to shoot you past that instantaneous balance point - but it might mean that your nutrients could decrease over time in general and the balance point could shift such that the scrubber is operating past that balance point, but that takes time to occur. Hope that makes sense. So @b4tn what you're looking at it that you are likely operating the scrubber well below the set-point for your system, and have been for a while. But, you have a mature scrubber, so you don't have to worry as much about creeping up on that set point. You can jump to the 4 o'clock position and 12 hrs/day, no problem, IMO. Then give it about 4-5 days and verify that your growth is coming along well (i.e. no new bare spots on the screen, no white spots where algae has died off right in front of one of the LEDs, etc). If everything looks good, then bump the intensity up to 3 o'clock and the hours to 16. Give it an additional 6-7 days to grow (so 10-11 days total). Then do a partial cleaning. Only remove about 50% of the growth, you can use the scraper, but "drag" it, instead of "chiseling" with it. Then put it back in at the same 3 o'clock / 16 hrs. Give it 3-5 days to grow, verify it's growing OK still. If it is, then (this is specific to your tank) jump to 2 o'clock and 20 hours. Now leave it here for another 10 days (14 days of total growth period) Hopefully by this point, your tank algae will have taken a beating. You can potentially get more aggressive with the ramp-up, but just pay attention to the growth to make sure you don't skyrocket past the balance point.