Go with TMaier's suggestion. I had the same issue with pH. Your playing with fire with such a low pH, as most if not all BB, will die, causing you to lose your cycle. I've been using Aragonite, and it's awesome, pH has remained at a constant 7.4 and things are going great! I am using about 1.5 cups in my canister. Just remember to rinse, rinse, and rinse to remove small dust particles, otherwise, the tank will turn cloudy.