If you haven't been checking your Reagent before you use it to make sure it's good do it now. Both of mine were bad. So I have been accurately correcting my tank to bad readings from my Alk Reagent. LOT 5423 IS BAD Go to this link and enter your Lot number. https://hannainst.wufoo.com/forms/w1hzjs2j1b4ejyu/ Guess I need to break out my Red Sea Test.