Water quality factors can affect fish health and production. Temperature, pH, alkalinity, hardness, and dissolved oxygen are rarely constant and will even change or cycle each day, while others like alkalinity will change over longer periods of time.
Oxygen is cycled through water in two ways- air and photosynthesis. Wind and wave action dissolve oxygen naturally into the pond water as the two mix together. PHOTOSYNTHESIS is the other cycle of dissolved oxygen and the most important. Here, plants produce oxygen from carbon dioxide, water and sunlight. Since oxygen production occurs during the daylight hours, dissolved oxygen levels tend to rise throughout the day and slowly decline at night as fish, insects zooplankton, bacteria and algae consume oxygen through respiration. Aerators can be used to increased dissolved oxygen levels during times of low oxygen.
ALKALINITY, HARDNESS, and pH
In order to provide an adequate natural food supply and a healthy fish population alkalinity and hardness are very important. Alkalinity is the measure of bases in the pond water and reacts to neutralize acids which directly affect pH. Hardness is the measure of calcium and magnesium ions present in the pond. a lack of hardness can reduce plankton production and can causes muddiness. The pH scale measures the acidity, which is formed from the carbon dioxide that is released during respiration. This carbon dioxide reacts with water to form carbonic acid. As carbonic acid is formed the pH levels are lower and the pond becomes more acidic. During photosynthese, algae uses the carbon dioxide increasing the pH levels and the pond becomes less acidic. The only practical way to control abnormal pH changes is to increase the alkalinity of the pond.