GaryP also had a good point in one of my threads. Just because you kit does not detect it does not mean phosphates are to blame.
I may be misquoted here or maybe its just a typo.

What I said was that just because your test kits shows 0 ppm phosphate, it doesn't mean that you don't have phosphates. Not all phosphates are detected by a test kit. If you are having a hair algae problem, its proof positive that you have a phosphate problem. It won't grow without phosphates. On the other hand, your corals and other do need some phosphate so you don't necessarily want 0 phosphates, not that that is even possible. As long as you are feeding your tank and fish are excreting waste you are going to have phosphates.

Gary