I have been using sodium hydroxide for a while now. I have a special setup, but the idea is the same. I have a whole home RO system that feeds my entire house, including my fresh water top off and my salt water mixing station. Using a peristaltic pump wired to my RO, any time my RO runs the pump runs and injects sodium hydroxide to my water. The pH of my water runs about 9.5, so every time I mix new salt water or my ATO comes on, it's pumping high pH water into my system. The CO2 level in my tank room is about 550 on average, and my tank pH maintains about 8.5. I purchased the 5 gallon jug of sodium hydroxide from a local water treatment company for $250.00. Feeding my whole house and tank, should still last me about a year or more.