| The trouble with baking soda is that it reacts too fast. Add baking soda and your pH will change immediately. In my opinion, calcium carbonate from oyster shell or coral rubble is a much better buffer. It reacts more slowly and will stabilize at a lower pH.
Larry is right on about the combined effect of baking soda and other buffers already present in your water. Baking soda will not help if you are trying to lower you pH. All it can do is immediately raise your pH.
For many high-end koi keepers, a KH of 100 to 120 ppm is too high to develop good beni and they shoot at something like 50 ppm. But, at 50 ppm you must monitor the situation most closely because you are operating closer to the edge of alkalinity depletion.
-stevehopkin |