I have been doing the usual quite hard back algae removal from my screen at each harvest until recently. I grow mainly Ulva intestinalis on the screen of my Atlantis 2 waterfall ATS and have changed how I harvest it. I now trim the algae back with some scissors giving it a haircut to within approximately 1" or so back to the screen. My thinking is twofold, firstly this seems to make the Ulva grow even faster as if it didn't grow fast enough after a hard screen back harvest. my Ulva can be harvested again in 5 rather than 7 to 8 days as when I clean my screen hard back. Secondly, there should be less of a rollercoaster ride with nutrients not that I think nutrient fall and rise would be that much with hard pruning back anyway but anything that aids stability has to be a good thing. Would this way of harvesting work as well with GHA? I don't really know but it should do providing it is reasonably well attached to the screen. Perhaps you could try it if it's not been done before and report back on if it works well. I have found Ulva grows at a rate of approximately 25mm in 24 hours. Here is a pic of my screen following the first trimming back of the Ulva. This was taken after I had seeded my virgin screen with Ulva and after 8 days growth. I will take another on Monday 5 days after I first trimmed the screen to show how much it has grown since.