Green Water
An outdoor pond will never be totally free of algae, nor should it be. Algae serves as a source of food for many micro organisms and is a critical part of the food chain.
Green water is caused by single-celled free-swimming algae. They are individually microscopic but may be present in such numbers as to make the pond appear as though it were filled with pea soup. Their existence depends on the presence of light and nutrients (primarily phosphate and nitrate) both of which are abundantly available in a newly filled pond in which plant growth is still relatively undeveloped. As the pond plants mature they will provide shade for the water and begin to absorb the dissolved nutrients required for the algae to survive. The algae begins to die and sinks to the bottom where it is eaten by the fish. The water clears, and it very often happens abruptly. There is no “normal” period for this; it depends on many variables… water chemistry, plant density, livestock levels, seasonal weather… that are different for every pond. Water changes will not accelerate the process. They may alleviate the problem temporarily, but in reality the newly added water is rich in nutrients which merely serve to start the cycle again. Plants and patience are the answer to most green water problems.
Brown Water
Murky brown water is the result of muddy sediment being stirred up by fish or by water turbulence. It may have a greenish cast because such stirring tends to encourage algae growth. The sediment must be allowed to settle and then be siphoned off or removed by filtration.
Milky Water
Milky, clouded water indicates decay and water pollution. It is caused by the decomposition of organic matter, particularly of fleshy origin. Change the water and search for the source of the problem; usually a decomposing fish.
