Build Your Own Pond Filter – Tips For Do It Yourself

Without a doubt, the garden pond is a visual highlight in any garden. Whether as a residence for koi carp or in larger dimensions as a swimming pond: a garden pond enriches a garden immensely and is a very special showpiece.

Basic information about the do-it-yourself construction of a pond filter

In order to keep the garden pond permanently attractive, it is essential that it is subject to regular maintenance. The most essential element for proper care is the pond filter, which ensures good water quality and clear water. However, the purchase of a powerful pond filter is associated with considerable costs. Many garden owners therefore shy away from maintaining their own garden pond.

A good alternative to a commercial pond filter is the self-constructed variant of a pond filter. Here, a large part of the purchase costs for a commercial pond filter can be saved. For example, with a so-called barrel filter, which is a widespread variant among the self-built pond filters. This is already used thousands of times and proves itself again and again by a high reliability regarding an excellent water quality.

In principle, when building a pond filter yourself, it must be individually adapted to each garden pond. Various parameters play a decisive role here. For example, it must be taken into account which substances must be filtered out of the water by the filter and in what quantities. If a garden pond is designed for keeping fish, it will contain different substances than a so-called swimming pond, for example. A pure plant pond, on the other hand, has completely different substances that need to be filtered out.

Other important parameters in the design of a pond filter are the respective pond volume and the flow rate through the individual filter elements. If the speed is not planned correctly and the water remains in the filter for too short a time, the filter will not be able to fully absorb and filter out the substances. As a general rule, a good pond filter should have the water contained in the pond flow through it completely once within one hour.

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Materials needed and general tips

The following building instructions give tips for the implementation of a pond filter, which has a filter volume of about 100 liters and which is suitable for a garden pond with a water volume of ten to twenty thousand liters of water. For the construction of the pond filter here 5 rain barrels with a volume of 200 liters are needed. Furthermore, various HT pipes and HT elbows, various rubber seals and brushes are used. For the actual filtering process in the pond filter, coarse and fine filter mats are used, as well as lava granulate, basalt or gravel.

The actual pond filter consists of five different stages. Each of the five required barrels forms a stage, whereby the water is fed into each of the water barrels from above. The water then flows in the homemade pond filter from the top to the bottom, then back to the top, and then in the next stage flows into the subsequent of the five barrels. After flowing through the fifth and final barrel, the filtered water is then returned to the garden pond.

  1. HT pipes are used to connect the individual barrels with each other, for the use of which it is necessary to create appropriate cutouts in the barrels.
  2. The cutouts should be placed as close as possible under the edge of the barrel and then fitted with rubber seals.
  3. The individual pipe sections are then drawn in as connections, whereby a barrel spacing of 5 cm each has an optimal effect on the
  4. later functionality of the pond filter.
  5. The individual connections are then placed inside the barrels with a 45 to 75 degree elbow, a pipe extension to the bottom of the barrel and a final elbow.
  6. In the first barrel there is a connection of the pond to the pond pump through a hose connection, with the UVC filter necessary for sterilization of the water placed in between.
  7. When placing the barrels, make sure that they have a slight slope to each other, with the following filter stage sits lower than the one that goes before.
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Structure of the five stages of filtration

The first of the five barrels does not contain any filling with filter materials, as this is only to set the pond water to be filtered in motion. Even here, however, coarse dirt particles settle to the bottom of the barrel. The second barrel is to be filled with brushes, which must stand vertically in the barrel. So many brushes are to be used that they can get jammed inside the barrel without additional fasteners. This filter stage also retains coarse particles as the water passes through.

The third of the total of five barrels is to be fitted with coarse filter mats. These are placed in a vertical position inside the barrel. To fix the filter material, spacers are required, which can consist of the strips of shredded coarse filter mats. In principle, the mats can also be placed or laid close to each other in the barrel. However, in this case there is a risk that the pond filter will clog all too quickly. More frequent cleaning of this filter stage would then be the immediate consequence.

Granulate – such as lava granulate – is used to fill the fourth barrel. Basalt rocks or gravel stones can also be used. It is important to ensure that the individual stones do not have a diameter greater than 1 to 2 cm. A higher grain size would have a negative effect on the later functioning of the pond filter. Finally, the fifth and last filter stage is equipped with fine filter mats. These must also be placed in a vertical position and fitted with spacers. This is the only way to counteract the previously described effect of this filter stage becoming clogged too quickly.

Things to know about building your own pond filter in a nutshell

  • Pond filters consist of a mechanical and a biological filtration.
  • A pre-filter acts as the mechanical part. It removes coarse impurities from the water.
  • In the biological part ammonia, nitrite and nitrate are transformed and decomposed.
  • In addition, a chemical stage can be installed to bind phosphates.
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There are two ways to build your own pond filter, one is the filtered and the other is the gravity variant. In the first variant, one pump moves the water into the filter. The second variant allows the water to enter the filter by gravity. A pump behind the filter pumps the water back into the pond.

Pumped pond filters are above the water level to prevent the water from backing up.
Gravity pond filters are below the water level to allow the water to run back.
The pond filter should be given a shaded location so that the water in the tanks does not heat up excessively. When building a pond filter system, the timing should also be considered, as algae formation begins as early as spring. If the pond filter is turned on in time, the formation of algae can be prevented.


  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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