Another part of the downward trend in pH is the result of organic acids produced by biological activity, especially bacteria. Compounds such as acetic acid (vinegar) are produced by bacteria digesting excess nutrients. While not real strong acids they do add to other factors pushing the pH down. The organic acids are neutralized by the buffering action of the water and can actually add to the overall buffering capacity. Farley Holmes recently wrote am article recently where he showed the buffering capacity of sodium acetate (neutralized acetic acid).
Remember that buffer, in the form of carbonates, is constantly being removed by corals and other critters in your tank and needs to be replaced. Buffer can also drop drastically if your calcium is to high. Calcium and Buffer must be properly balanced. OK, enough for now. I think I just ruined my talk for this weekend.
Gary
Gary
125 SPS, 75 gal. LPS/softie reef, 9 gal. Nano