My phosphate is now 1.0. This was after a 15 gallon water change on my 55 gallon tank with 55 lbs. of liverock. Sometimes it's difficult to tell whether or not my phosphate levels are 1.0 or if they are 5.0 because matching the color of the vial to the color on the phosphate chart is difficult. I don't put the vial against the chart but hold it a few inches away.