I had bad luck with my scrubber with same design I found on YouTube a while back. The first problem was the LED light gave me poor algae coverage on my very roughed up screen so I switched to compact fluorescent and bam! The algae started covering the whole screen but I only used one light on my screen and the instructions I found recommended using a light for both sides for effective scrubber but I had limited space so maybe that's why my nitrates weren't dropping. I still gave it another month which I had some algae like you would find growing on the back glass so I got excited but nitrates were still up. A week later I had a power outage that dried out my screen completely :( so all that break in period wasted and the smell from no water on it was horrible. So I didn't feel like going through this again so I kept my sump and threw some chaeto in there which a week of the chaeto brought my nitrates to zero. I really wanted to use the waterfall algae scrubber but just didn't work for my situation. Gotta say though try the compact fluorescent bulb you'll get 10 times faster algae growth and they are super cheap to run.
