Here are a few pics of what my screens look like post-harvest, hopefully this helps you see what I mean by removing the brown gunk/mulm The point it, if you can see some of the white/plastic clearly exposed, this is not necessarily a bad thing. You just don’t want to intentionally scrub it so that it all looks like that Let’s say you haven’t ever rinsed the screen - you might end up with a layer of this brown growth that is actually somewhat firmly attached, and refuses to come off with a simple rub/rinse type of cleaning. In this case you may actually have to use a brush. But not the stiff bristled one, only use that in the top edge (where the screen was not roughed up or coated with mortar) Use the soft-bristled denture toothbrush and lightly swipe it across the screen (in a dragging motion vs a back & forth scrubbing motion) while rinsing under room temp tap water. Start with very little pressure, make a pass across half of one side of the screen then compare before/after. It should look like more of a mixture of white & green, similar to the pics above, but that might take a few growth cycles to get it looking closer to that. Hope that helps!!