I don't even knpw where to begin. But this has dumbfounded me. I'm using Brightwell Neomarime and RODI which always mixes to about 7.4 dkh for me. Suddenly in the last two months, and despite switching to a new bucket of salt, I mix up a 5 gallon batch and the alkalinity is 5.8. After several attempts to change the way I mix I get the same result. Last night I decided to use soda ash to up the dkh to 7.8 (+2 dkh) in order to do a water change and I wake up this morning and the result was 4.8 dkh. I used a different hanna checker and a new reagent and the result was 4.9 dkh on that test. I am using a pump to keep water moving throughout. It does generate some heat in the water due to the pump I believe (it's also quite an old pump). Does anyone have any idea what coukd be happening or what I could be overlooking? I am totally stumped!