Stay away from the Marine Lab saltwater test kit from Red Sea Pharm. Nobody on this board likes the test kit and I found out why. Basically the test kit said my Ph was extremely high and my alkalinity was very low. Well, i kept doing water changes to fix the problem and it never seemed to fix it. I also buffered the tank every day to hopefully raise the alk. Well, I basically destroyed my tank because it turned out that my alkalinity was so high that it was off the scale. It also turned out that my Ph was fine. I know this because I finally got the brains to have my water tested by somebody else. Too late though. All my corals died. My fish lived though. Just stay away from that brand of test kits.