Water Quality

WATER QUALITY INFORMATION

The most important element of a successful water garden is water quality. Some people start a water garden with the idea of a "natural pond". What you must understand is that the average water garden is far from natural. It is totally man made, containing a small volume of water, and dependent upon the pond owner for such things as water changes, population control, food source, cleaning, and filtration. In a natural body of water, nature performs water changes by streams constantly flowing in and out, by runoff from rain, or melting snow. These bodies of water are cleaned by periodic heavy rainfall literally "flushing" the system. If there is an extended drought these natural ponds will even suffer water quality problems the same as man made ponds when neglected.

There are several things that must take place in order to achieve a healthy balance in your pond. I'll give a short explanation of the nitrogen cycle, and post links for more in-depth explanations.

NOTE: Anyone getting involved with water gardening should obtain a water test kit with test for pH, ammonia, and nitrite. These are the minimum test. To have a better understanding of your water parameters you should also get test for total hardness, carbonate hardness, and nitrate as well. Clear water does not automatically mean it is healthy!

A pond is an independent ecological system. If everything was perfectly in balance we could start with a new pond, add our fish and plants, and go full circle around the nitrogen cycle to obtain zero (0) nitrogen in the water. But our enclosed system cannot break down the wastes as fast as they are being produced.

Feeding our fish creates waste. The waste is converted from bacteria to ammonia (NH3). The ammonia is harmful to fish and can be deadly, but bacteria consume the ammonia and break it down into nitrites (NO2-). The nitrites are also toxic to your fish. Fortunately another type of bacteria will develop in your pond, and will consume the nitrites and produce nitrates.

All of the bacteria that participate in this cycle are aerobic; meaning they need oxygen to survive. Without oxygen, anaerobic bacteria (needing no oxygen) develop. The anaerobic bacteria will convert nitrates and phosphates into methane gas. Solid wastes left in the pond help the anaerobic bacteria thrive. The biological process, even if it is a biological filter, does not rid the pond of solid wastes. A mechanical filter should be used for this process.

Plants are used to combat algae. Algae will use up excess nitrate and phosphates, converting these into more plants, which is why your pond turns green. If you have ornamental plants they will use the excess nitrates and phosphates before the algae can, eliminating the green water. Floating plants such as water hyacinth, frog bit, water lettuce and parrots feather are some plants that grow quickly and use the extra nitrates and phosphates before the algae. The submersible plants like anacharis and hornwort are also good plants to head off algae, and supply additional oxygen to the water. If you have at least 50-70% coverage on the surface of your pond it should stay free of algae.

Dynamics of a Fish Pond, by Chris Neaves

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Last modified on Tuesday February 15, 2000