Hmm... Yeah it do look like diatoms, I tried to give the screen I quick wash, the brown stuff rubs right of
I get this from time to time also - thin brown layer over the green hair. Not always. Smells putrid but once it is "swiped" off, no smell.
I am thinking, its a little boring looking at the same over and over.. Any good ideers fore spicing the videos up , maybe add some commentating? or action replays?
You might try letting it grow for a longer period of time. Growth looks pretty thin, so it's not blocking much. What I would do is just an "intermediate" cleaning...take it out at 7 days and "drag" the scraper across the screen to remove any loose algae, then give it a rinse like you currently do, and re-install it and check it again in about 3 or 4 days. The only reason I say this is because you have stated that you have 20-25ppm nitrate, so you want to leave the good green base of growth on the screen longer to allow for thicker growth, which occurs over time. Scraping the screen clean off every 7 days will slow the nutrient uptake slightly, it may or may not make a huge difference with your growth, but it definitely won't hurt to let it grow longer. FYI I usually let my screens grow 14 days between cleanings. Sometimes by the 14th day they are really thick, and all green, right down to the screen. The 'denser' the growth, the thinner it seems to be. I get growth like you are getting on one of my tanks pretty consistently at around the 7 day point, but by 14 days it has thickened up quite a bit.
Let go 7 days, then do intermediate cleaning, then again on day 10 or 11. At day 10 or 11, you can scrape if you want to, or just do another intermediate cleaning and let it grow to day 14. But at day 14, I would scrape it. The point is that as long as the growth is not thick enough to block light and cause lower layers to decay, let it grow longer.
If your gonna mess with the screen every week, why not just clean one side? I found it helped with regrowth
Well, you'll find that light inhibition (the thickness of growth that prevents light from penetrating, therefore halting photosynthetic growth) is stated on the scrubber site at around 20mm. This is cobblers in a unidirectional waterfall scrubber. I found by tests that around 5mm (4 days growth) is the limit of light penetration. Independent professional biologists found it to be around 2mm in natural situations at full light intensity at depth, so I'm not a million miles off. One sided cleaning may provide valuable light to the unharvested side of the screen. Rambling, sorry
Or clean in cross-patterns, like this In this example, I scraped in lines one way on one side, one way on the other side
