Phosphate test kits can be a bit tricky. Here's why:
Without going into a lot of chemistry there are two kinds of phosphates. A lot of folks eyes start to glaze over when I start lecturing on water chemistry. One kind of phosphate is detected by a test kit, another kind isn't. There is not really such a thing as "good phosphates." While a very small amount is required in your tank, this level is practically zero (about .02 ppm). Fish and other critter eat foods and excrete the phophates contained in them as phosphates. Most of what is excreted is not detected.
Gary
Gary
125 SPS, 75 gal. LPS/softie reef, 9 gal. Nano