Water quality parameters and lake management go hand-in-hand. Alkalinity and hardness are important in providing adequate natural food and in maintaining a healthy fish population. The pH of lakes and ponds cycle daily because of respiration and photosynthesis. Carbon dioxide released from respiration reacts with water, producing carbonic acid. The pH scale measures the acidity therefore, as carbonic acid is formed the pH is lowered or the pond becomes temporarily more acidic.
Algae use carbon dioxide for photosynthesis during daylight hours and the pond water becomes less acidic with the decline of carbonic acid. Because of this, lake pH normally fluctuates between 6.5 and 9. If the pH drops below 5, as it does in lakes and 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 lake or pond.
Alkalinity is a measure of bases in the water. 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 ions. Hardness concentrations are usually similar to alkalinity (if derived from limestone) but can be different especially in coastal areas. A lack of hardness can reduce plankton production, cause muddiness, inhibit fish growth, and undermine your whole lake management program. As you can see, monitoring water quality is very important for the success of your lake and its fish populations.
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