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 .
Planktonic algae serve as the base of the food chain.
Small fish are then eaten by larger fish. Directly or indirectly, algae provide almost all the basic food for the pond except for a small quantity of insects and worms that fall or wash into the pond. Managing planktonic algae is essential in providing the food to produce an abundant and healthy fish population. When this happens, decomposition of the dead algae consumes oxygen, leading to possible stress, suffocation, or disease. Mechanical aeration may be necessary after algae die-offs to keep fish alive.