Just another quick update... It's been one week since I added the last 4 oz of PR10000. The phosphates are right at 200 ppb. The effectiveness of this Orenda product is no where close to what's indicated on the label. Anyway, I'm done for this year. The water temps are down in the mid 70s and the yellow algae still returns, but much more slowly than before. After brushing, it takes about 3-4 days to notice the algae (vs 1-2 days previously), and it's a much smaller growth than before... probably some combination of lower phosphates and lower temperatures. FC consumption is steady at 2.5 ppm per day. My cartridge filter pressure is at 19 psi, up from 12 psi after the last cleaning in May, which is maybe 2-3 psi higher than it would normally be, absent any phosphate removal process.