I currently have a 90 Gallon SPS tank. I originally was running GFO and had issues because I was at 0 and I watched a lot of my SPS start to STN from the tips basically starving them. Since then I took the GFO off line and things have been going a lot better. Now my phosphates are at 0.33 with a hanna tester. I would like to bring them back down to between 0.05 - 0.10. I have been doing 5 Gallon water changes per week and that drops it down to 0.25 but it keeps creeping back up. Should I do larger water changes? Any suggestions would be greatly appreciated. I would prefer not to start GFO again.