Carbon dioxide released from respiration reacts with water, producing carbonic acid. Algae use carbon dioxide for photosynthesis during daylight hours and the pond water becomes less acidic with the decline of carbonic acid. If the pH drops below 5, as it does in ponds that receive acid runoff, or rises above 10, as in low alkalinity ponds with excessive algae blooms, fish will be stressed and can die. The only practical method to manage for abnormal pH changes is to increase the alkalinity of the pond. Bases react to neutralize acids and, therefore, directly influence pH. As bases react with the hydrogen ions present, they buffer or suppress pH changes.
Some alkalinity is necessary for good algae production.
An alkalinity of 20 ppm or more is necessary for proper algae growth and, therefore, good fish production. Hardness is a measure of calcium and magnesium ion. A lack of hardness can reduce plankton production and increase the likelihood of muddiness. Pond Color Plankton is a term used for all microscopic and near microscopic living things that float in the water. Plankton includes both tiny aquatic plants called phytoplankton or algae and animals called zooplankton .