i finally bought my first salifert test kits. i have been using red sea calcium and all test kits. all i can say is my tank was a little out of whack. my red sea showed my calcium to be around 400 or so...my salifert shows that it was actually 370. my alk showed to be 3.3 on red sea but salifert showed it to be 2.9 or so. glad i switched test kits.