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The Greener View: Healthy Ponds

Jeff Rugg on

Question: How much water should I circulate in my water garden? I read conflicting reports saying to add more water anywhere from once a day to once an hour. I want the water to be clear, and I do have some goldfish in the pond, with a few lilies and other plants. My pond holds about 1,800 gallons.

Answer: This is a common question with a variety of answers. The answer is not based on the size of the pond but rather on the style and use of the pond. The first thing that must be asked is what your purpose of circulating water in a pond is. Most people have two reasons. First, they want to have a pretty water feature of a waterfall or of a fountain. Second, they want the water to be filtered so it looks clear and is safe for the pond inhabitants.

To create a pretty waterfall, we need to know what a person thinks is pretty. For many people who are creating a backyard basic water garden, a water flow of 100 gallons per hour for each inch of waterfall width will create a nice-sounding and nice-looking waterfall. This flow will be about one-quarter of an inch thick. To create a noisier and crashier flow of water, you would need to go one-half of an inch thick or more. Since this prettiness part of the equation is very subjective, it is best to actually look at existing waterfalls that are being run with a pump of a known capacity to be sure of what you want. The same holds true with a fountain; it is best to look at an existing one to see if it is the proper size and prettiness and then find out what size pump is being used to create it.

For the filtering portion of our equation, we need to look at the two major types of filtration. Filters can be used to remove the large, visible pollutants in a pond (mechanical filtration) and to remove the invisible pollutants (biological filtration). Skimmers are typically used to remove the large, medium and small particles as they float around in the pond. Properly designed skimmers will not send particles to clog up the biological filter where the invisible chemicals are to be removed.

The properly sized skimmer would pull enough water in to the nets and filter mats to keep the water clear of floating debris. The properly sized biological filter would keep up with the amount of pollution being created by the fish and other animals and the breakdown of any organic matter. Typically, for many water garden ponds, the amount of water desired for the water feature effect is more than enough to keep up with the two filtering needs.

Most backyard ponds have more fish in them than similarly sized amounts of water found in nature. In a natural situation, the natural chemical processes work because there is a great amount of dilution. The smaller the pond, the larger the pollution load on the filter system from the same number of fish, so the water ought to go through the filters more often in a smaller pond.


A water garden will tend to have a lot of plants and other biological components like gravel and bacteria. At first, when a pond is installed, the fish are small and do not require much filtration. Over time, the fish grow, but the filter system does not, so ponds with small filters depend more and more on the other ecosystem components to make up for the filter's deficiencies. Water gardens with large volumes of gravel, lots of plants and bacteria, and few fish do not need large pumps circulating the water. Water volume turnovers of one to five times are often created by the waterfalls and are more than enough to handle the mechanical and biological filtration needs of the pond. The larger the pond, the lower the number of turnovers necessary, unless there are too many fish, in which case the extra filtration of more turnovers will help.

Buying a kit where the manufacturer has specified all of the components is a good starting point for determining the proper size of pump and filters necessary.


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