Garden Pond Water Quality

Maintaining a Delicate Balance

Maintaining a healthy outdoor garden pond starts with understanding water quality. Pond owners need to understand that water clarity and water quality are two entirely different topics. Water, like your tap water, can be crystal clear and still kill the aquatic life in your pond. On the other hand, cloudy water can provide a healthy environment for your fish and plants. As you set up your garden pond, make sure that the water is as healthy as possible.

The Nitrogen Cycle

Understanding the nitrogen cycle is the first step in maintaining clean water in your garden pond. Every self-contained aquatic environment, like a pool in your garden, has the nitrogen cycle. When your fish create waste products, bacteria and fungi in the water convert it to ammonia. This ammonia can kill your fish, but when the pond has the right balance of bacteria, some bacteria convert the ammonia to nitrites. Nitrites are also toxic, but yet another strain of bacteria converts the nitrites to nitrates, which cause no harm to the fish. The nitrates, however, are necessary for the plant life in the pond, which then provides food for the fish to start the cycle over.

A pond that has poor water quality will have high levels of ammonia or nitrites. Testing the water with a water chemistry testing kit can help you determine if this is your problem. If you notice high levels of ammonia or nitrite, use a commercial treatment to get these toxic elements under control. Then, encourage the growth of biological bacteria with a quality bio-filter. Avoid cleaning the bio-filter with tapwater, because doing so will damage the balance of helpful bacteria in the water.

Chlorine

If you are using tap water, such as water from your garden hose, to fill your outdoor pond, you will have to battle chlorine. Most city water is treated with chlorine and other chemicals to remove harmful bacteria. While this is important when drinking the water, that same chlorine is toxic for fish. Always add declorinating drops or tablets to the water before adding it, and do not run garden pond water features using pure tap water that has not been pre-treated. It is far better to run the water features using water recycled from the pond itself. This will not only prevent the introduction of any toxins into the pond, but it will also provide aeration to the water.

Water pH

Another aspect of water quality is the pH level of the water. Most outdoor garden ponds that have Koi as the main feature fish need a pH in the range of 7.0 and 8.5. A pH below 5.0 may be tolerable to the fish, but will likely damage the helpful bacteria in the water.

Regularly test the pH of your garden pond water. As long as the water is within this desired range, you can leave it alone, but avoid doing anything to the pond that will increase or decrease the pH substantially. Too many water changes will cause these fluctuations, and frequent changes in pH cause unwanted stress to the fish. On the other hand, if your pH is not in the desired range, do daily water changes of 10 to 25 percent until it stabilizes, or use a good quality pond pH buffer.