Over the last couple of weeks, the Ulva intestinalis that previously grew at an incredible speed has subsided greatly to the extent it went from around a 410gramm harvest to just a couple of grammes. What I can only describe as a compact dark spongy moss type algae have taken over where the once Ulva proliferated. I have just completed some tests, My NO3 is between 0.05ppm and 1ppm, my PO4 is 0.015ppm. Once in a while I dose a little iodine and have recently been adding a small amount of iron twice a week.All corals are as well looking as they have ever been with vibrant colours. For example, a Forest fire which had lost it's colourful yellowish tips has come back wonderfully and all SPS corals are growing at a fast rate. Are my nutrients now too low as when I started with my Atlantis 2 scrubber my NO3 was 20ppm and my PO4 was 0.04ppm? I have just cleaned off the screen (both sides) using an old credit card scraping right back to the screen and rinsed under tap water, then reseeded with a little Ulva so will see what grows back the strongest. Pic's of both sides of the screen.