I just started running GFO in a reactor. I have struggled with high phosphates pretty much (0.3-0.5 per hanna). Tank is about 2 yrs old now. I really want to get my few corals growing instead of struggling and eventually add some. Also my clean up crew's not able to keep up with the hair algae. Anyway, I started the GFO on 12 /29. In 24 hrs phosphates went from 0.4 to 0.21. The next day, Jan 1st, they were 0.15! I was so excited....till I just tested today and I'm back to 0.3! Surely I don't need to change it already... my weekly water change day is Thursday, so it's still a couple of days away.