Phosphate slowly rising started at .04 then .08 then it hit .14 so I do a water change, test the next day and I’m at .34. This has all happened in the past 2 weeks. My question is should I use some gfo? only reason I’m thinking gfo is my nitrates are getting lower due to water changes. Which is not lowering phos. Nitrate at 4.4 right now.