>Sodium bicarbonate does not increase the "total hardness," which is a goofy >term for the total amount of Mg, Ca, Sr, and Ba ions in solution. It does >increase the "carbonate hardness," or alkalinity, and does increase the >buffering capacity of the water, but this buffering is not permanent. The >bicarbonate can be converted to CO2 by acids such as the peat acids. I thought that the total hardness was the combination of the carbonate hardness and permanant hardness. I believe that increasing your carbonate hardness will increase your total hardness by definition. It is my understanding though that carbonate hardness can be reduced by boiling or other procedures to break down the carbonates. Mike - ------------------------------------ Dept. of Ecology & Evol. Biology, MS-170 Rice University 135 Anderson Biology Lab 6100 Main Houston, TX. 77005-1892 Ph: (713)527-4919 fax: (713)285-5232 e-mail: henshawm@ruf.rice.edu