I'd like to throw this question out there because I'm still trying to research the answer. Maybe one of you guys can help me out. Been checking my phosphate levels with the Elos test kit all this time not knowing my phosphates were up there. Checked my phosphates on a hannah checker and read 0.15ppm! I was reading and found out that the manufacturer will tell you that your results will very +/- .04ppm.http://www.hannainst.com/manuals/ist713_02_04_10.pdf So I go and check it with the D-D test kit. I believe my phosphates are around 0.05ppm-0.09ppm. Now my question.....is this a high enough reading to hinder the calcification of some of SPS?