Aquaponic Systems that are operating in an aerobic condition, the nitrification which converts Ammonia into Nitrite then Nitrate, has a continuing falling pH. Therefore a buffer must always be added to keep the pH at an ideal 6.7 to 7. It is the addition of these buffers that can allow the operator to add a Potassium and or Calcium buffer. Both elements are always missing in an aquaponic model. Fish do not require the same amount of these 2 important plant nutrients, Potassium- K and Calcium- Ca. You will never find these two elements in fish foods. Therefore it is never added to the tank unless added over and above the food given to the fish. So these two elements should always be used to adjust pH in aquaponic systems instead of another form of an alkaline buffer.