Definitely wasnt test kits or salt mixing. When I purchased the salt from two guys Coral JW told me I might want to mix the salt around in the bag for a few minutes before using. So I did. Tossed the bag around, used a stir stick and still had inconsistent calcium and alkalinity but as I got to the bottom the bag the results were more consistent. So, Im pretty sure he knew it was either a bad batch or he was having same issues.