When there is a strong algae bloom, the pH has a significant variation with time of day, since plants produce acid at night and consume acid in the daylight hours. So if there is an algae bloom, the pH will maximize at sunset and minimize at sunrise. In my own ponds, when I had a green algae bloom (before UV lights and trickle tower filters!), the pH would dependably be 5 at sunrise and 10.5 to 11 at sunset. When this occurs, massive addition of baking soda can sometimes reduce the pH bounce somewhat, but not eliminate it.
So if you have a significant algae issue, you must first measure five things before making any decision about pH control:
1. pH near sunrise
2. pH near sunset
3. KH or total alkalinity at sunrise
4. KH or total alkalinity at sunset
5. GH at sunset
If total alkalinity is below 100 ppm (morning and evening) and pH is dependably high (morning and evening), first add one pound of baking soda per 1000 gallons, wait a day, then add one pound of calcium chloride flake per 1000 gallons. This should stabilize pH near 8.3 in the absence of a bad algae bloom.
If there is a bad green water algae bloom, then installing sufficient UV light capacity should solve the green water algae bloom and the pH bounce.
If there is a bad string algae bloom (frequently the case in Spring ponding, particularly in May), add sufficient hydrogen peroxide to bring the string algae under control and the pH bounce will stop.
Last edited by Roddy Conrad; 05-25-2009 at 08:09 PM.
President Truman said, "If you can't stand the heat, get out of the kitchen." And he said if you want a friend on the AKCA board, better take your dog to the board meeting with you.