The pH will fluctuate due to photosynthesis by the algae. During daylight hours, photosynthesis consumes carbon dioxide and releases oxygen. At night the process reverses. Carbon dioxide in water forms carbonic acid, which lowers the pH. With the reduction during the daylight hours of the carbon dioxide the pH increases and at night the process reverses. Even with large amount of baking soda, you will find slight changes from morning to evening, but they should be minor, which will help the fish and help the filter bacteria. The filter bacteria also produce carbon dioxide which for the first layers of bacteria is consumed readily by the KH, but as the depth into the filter media goes, the amount of KH available for consuming the acids is reduced and at low KH levels, can suffer from the low pH, killing the bacteria in those layers.
Zone 7 A/B
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