Learn how nitrification, oxygen, and bacteria all interact in your garden pond filter
Nitrification is the process of purifying the water in your garden pond. In this process, the ammonia in your pond water--which is toxic--is converted to nitrates, which are harmless to the fish and plants in your pond. This process, which takes place in your biofilter, must continue 24/7 or your pond will become unlivable for your valuable Koi or other fish. So where do this toxic ammonia come from? From your fish. As fish consume food and excrete waste products, these wastes (ammonia) quickly build up inside the closed ecosystem of a garden pond. In simple terms, your fish are living in their own toilet water. Now in a natural stream or lake, the concentrations of these harmful chemicals is relatively low. Naturally-occurring bacteria in the water, which cluster on rocks, plant roots, submerged trees, etc, all act to convert ammonia into relatively harmless nitrates. This works to keep streams and lakes in a health balance, and is why fish and plants in nature thrive. But in the closed ecosystem of a pond, there are no natural filters. That's where your biofilter comes into play. In the Basic Nitrification Cycle, the beneficial bacteria in your biofilter removes the ammonia almost as soon as it's formed. In this process, the ammonia is converted into chemicals known as nitrites. Then, another type of bacteria in the filter converts those nitrites into nitrates, which are much less toxic than either ammonia or nitrites. This is a continuous process inside your biofilter, and won't stop unless your filter loses it's oxygen supply. This is why your pump must be reliable and must be operating at all times, or the bacteria in the filter will quickly die. If your pond water is changed frequently, then the toxic levels of ammonia will be controlled somewhat, but you'll still need a biofilter system to insure a healthy pond environment. The amount of waste products in your pond will be directly related to the type of fish you keep. Be aware that Koi produce up to 3 times more waste than goldfish of the same size -- mainly because they eat 3 times as much. Another factor influencing the ammonia buildup of your pond water is the type of food used to feed your fish. Try to avoid foods that have a high ash content -- this indicates a low grade of food and will result in higher levels of toxic ammonia in your water. If you have a small garden pond, you can install a filter directly in the pond. For larger ponds, the filter needs to be set-up outside of the pond. As stated earlier, the pump supplying the filter needs to run 24 hours per day, 7 days a week in order to keep the bacteria supplied with oxygen. Another good idea is to install a fountain or waterfall in your pond, as these help increase the oxygen content of the water. Generally, the more oxygen you can get into your pond water, the better. Supra is a brand of biomedia that works well inside of pond filters. Supra is a bacteria that breaks down the harmful ammonia molecules in your pond water and converts them into nitrates, which serve as plant fertilizer for you pond. Again, oxygen is a necessary ingredient for this conversion process. If you measure your pond water just after feeding your fish, you'll notice a spike in ammonia levels. This is normal, and if your biofilter is working properly, this will quickly be brought under control. Supra is a superior product for use in your biofilter. In effect, 1 liter of Supra can hold the same amount of bacteria as 200 liters of plastic tubes. Supra looks somewhat like cinders, and is lightweight and comes in various sizes. For more on this topic, see the Supra and bacteria starter articles. |
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