I thought I had seen a waterfall scrubber thread explaining what to do if your screen looks like "this" or is a certain color, etc. but can't find it. I'm trying to determine how much to increase light or decrease light and time. Below is what my screen looks like after about 3 weeks lit for 18 hours. The screen on the Inside of the slot pipe where there is no light is a mix of green algae and what looks like cyano bright green slime. Any suggestions? Is there a thread on how to tune and maintain after building? Here is my screen so far.