If you want to drop phos without impacting nitrates too much, you can look at lanthanum chloride dosing. I've had some success with
Phosphate RX and the
10 micron socks. The nice thing is that you have fine control of the dosage by dropping exactly as much as you need. The 10 micron socks are necessary to capture the precipitate that is formed otherwise it might irritate corals/fish. I started off with 3 drops a day (eventually started doing 6 drops) directly into the filter sock to go from a phosphate of 0.5 to 0.09 over the course of a few weeks.