Measured the calcium after the water has set for a few days and it was approx. 490ppm. PH appears to stay between 8.0-8.1, before and after adding the supplement to raise alk, but my PH test has expired so that may be inaccurate. I don't have a magnesium test so that went unmeasured. The water is in a covered brute trash can, that I have been using for 6 months or more for water changes. What air are you asking about? I have the container in my laundry room. Id assume it gets decent air flow in there. I switched to the seachem salt due to some test numbers I saw over on RC, I was hoping to not have to dose anything to my water change water.Next time try to also measure the Calcium of that storage container to see if it has fallen also. Also, what has happens to the pH during this time and what is the Magnesium level ? If these are normal the container may be collecting organic acids and the buffer is trying to neutralize them. So, is it covered ? Where is it stored and where is the air coming from ?