I have noticed that ph has a tendency to creep back to where it started. Â If your ph is high out of the tap you will probably have your ph creeping up over time. Â If your ph is low out of the tap you will probably have your ph creeping down over time.
I'm not so sure I buy into this theory considering the chemistry. Â Of the sanitizers available (please correct if wrong), dichlor is the most benign re: pH with it's pH of 7.0. Â I use dichlor for sanitization and both dichlor or MPS (pH 3-4) for shocking. Â Out of the tap, pH is 7.5 for my water. Â After a water change, adding air and agitation causes the pH to jump to 8.0+. Â After initially adding dry acid to bring pH down to 7.8 or so, I find that pH will continue to drop, not rise. Â This makes sense considering that I am adding dichlor (pH 7.0) daily and either dichlor or MPS (pH 3-4) weekly to bi-weekly. Â After a while, soda ash is needed to bump pH back up. Â I would think that utilizing bromine would just exascerbate the problem since bromine is a bit more acidic than dichlor.