Last updated: August 7, 2021

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You want to build a pond in your garden? Or do you already have a pond and want to improve the water quality? Then you should find out more about pond filters. A pond filter keeps your pond clean and clear. Many pond owners can't imagine maintaining their pond without a filter. But what types are there? And how can you recognise a good pond filter?

In our pond filter test 2021 we present the best and latest models from various categories. We also give you important information on how they work and helpful tips. Whether you need a pressure filter, flow-through filter, underwater filter, bead filter, drum filter or fleece filter, you will find the best pond filters on the market.




Summary

  • A pond filter uses a pump to convey the water from the pond into a container with various types of filter media. There, impurities are filtered out in a biological and mechanical way.
  • The filter ensures that the depth of visibility and water quality in the pond are improved. This makes it a visually appealing, healthy habitat for fish and plants.
  • The most common types of filters are the flow-through, the pressure and the underwater filter. For an ideal result, the system should match the condition of the water body.

The Best Pond Filter: Our Choices

Guide: Questions you should ask yourself before buying a pond filter

How does a pond filter work and what materials are available?

When you create a pond, you probably also want your water to stay clear and free of algae, and to provide a healthy habitat for a possible fish population.

Whereas naturally occurring water bodies will eventually reach an equilibrium, with your garden pond - especially a fish pond - you will need to do something about it, i.e. install a filter for pond maintenance.

A filter system for water bodies usually consists of an upstream pump and a filter housing, often divided into two or three chambers.

The pump is placed just above the pond bottom and connected to the filter on the pond bank with a hose. The pumped water flows through several layers of filter material in the filter barrel and, cleaned at the end, back into the pond.

In a multi-chamber filter, first coarser dirt particles and then finer suspended particles are collected. In the last step, dissolved pollutants are biologically filtered by bacteria.

There are several possibilities as to which material you can use in your filter. Mostly the order of the materials is important. All of them need to be replaced or washed regularly to maintain the filter's performance. The following materials, among others, are often used:

  • Filter brushes: as the first filter stage for coarse debris
  • Filter mats: filter mechanically and biologically, rather high-priced
  • Japanese mats: consist of plastic threads, rather coarse-pored
  • Filter cubes: inexpensive, for biological filtration, provide a large settlement area for bacteria
  • Activated carbon: often in pellet form, as the last filter step, binds toxins such as nitrite or ammonia

The materials differ in their fine porosity, which is expressed in PPI. You may know this as "pixel per inch", but here it means "pores per inch", i.e. how many pores there are in an interval of 2.54 cm. The higher the PPI number, the fewer dirt particles can flow through. Coarse-pored materials, however, are easier to clean.

What are the advantages and disadvantages of installing a filter for your pond?

A filter is not absolutely necessary for every pond. To decide whether the purchase is worthwhile for you, the following advantages and disadvantages will help you.

Advantages of a pond filter:

  • Clear water: various contaminants such as algae, metabolic products of fish, and external inputs such as leaves are removed from the pond.
  • The environment is protected because no chemical cleaning agents are used, only mechanical and biological processes are used for cleaning.
  • Some devices can be used to operate streams, waterfalls or fountains.
  • Some filter materials remove toxins that are harmful to fish.

Disadvantages of a pond filter:

  • In most cases, a cable must be laid for the electronic parts.
  • Operating costs are incurred due to electricity consumption. These can be expected to vary depending on the filter system.
  • Noise pollution in the garden can be caused.
  • Maintenance: Filter medium must be replaced or washed regularly.

Teich

A pond filter helps you keep the water in your garden pond clean without the use of chemicals. However, the pond filter needs electricity and regular maintenance.

What is a UV pond filter or UV-C device and do you need it for your pond?

UV pond filters are colloquially referred to as all filters to which a UV-C device or UV lamp is connected. UV and UV-C are used synonymously in this context. One also speaks of a UV pre-filter, (pre-)clarifier or light filter.

UV-C stands for ultraviolet light

, especially with a wavelength of about 100nm to 280nm. Most UV lamps use radiation in the 200nm-300nm range.

What are the benefits of using UV radiation for your garden pond?

Especially if your pond gets a lot of sunlight, algae and floating algae will form over time and cloud the water. The pond then no longer looks clear, but greenish. Since floating algae are difficult to combat with normal filters, it is worthwhile to purchase a UV pre-filter. The

The UV radiation emitted by the lamp destroys algae by attacking their surface and causing them to clump together - the algae can thus be caught much better by the mechanical filter that follows.

In addition, the radiation also kills germs and pathogens such as bacteria and viruses. Unlike chemical agents (such as AlgenStopp), no resistance can develop against the UV radiation, so the effectiveness does not decrease. In addition to the optical clarification, the lamp thus also improves the water quality for fish.

How is a UV-C device used?

UV-C devices are integrated into a filter-pump system outside the pond. They are usually installed directly in the filter so that the water is first irradiated and then flows through the remaining filter stages. This is why they are also called UV pre-filters. It is important to choose the right lamp intensity for the size, location and fish population of your pond in order to achieve an optimal result.

After its service life of a maximum of 7000 to 10,000 operating hours (which corresponds to about one year of use), the lamp must be replaced. In autumn and winter, the UV-C unit can be removed: At cool temperatures, algae and germs can only grow poorly.

What does a pond filter cost?

How much you have to invest in your pond filter depends entirely on which system suits your pond best (more on the different types under Decision). The price also depends on how big your pond is and how many fish live in it.

You can buy filter systems as a set with a pond pump and UV unit, or individual filter units if you already have some of the equipment.

Some complete systems, such as pressure filter or flow-through filter sets, can be purchased in the basic version for smaller ponds for less than 200 euros. For others, such as bead filters, drum or fleece filters, you have to reckon with purchase costs ranging from 1000 to several thousand euros. For a very small ornamental pond, you can get underwater filters for as little as 40 euros.

Teichfilter

Pumps and an upstream UV-C unit require energy, depending on their output. So make sure you choose the right equipment for your needs to avoid high electricity bills. (Photo: Jastro / pixabay.com)

What should you know about cleaning and maintenance?

If the pond filter is working well, the suspended matter, dirt particles, algae etc. that it combs out of the water will gradually clog the pores. In addition, the filter bacteria that have settled on the filter material multiply.

All this damages the permeability and effectiveness of the filter. In order to maintain its full efficiency, you must therefore care for it regularly. The rule here is that larger filter systems need to be cleaned less frequently.

To clean the filter, first switch off the pump to stop the water flow. Then open the housing, remove the filter mats and wash them thoroughly with cold water. The best way to do this is with a garden hose. It is advisable to rinse and wring them out several times.

It is important not to use hot water or detergent so as not to destroy the bacteria cultures living in the mats. The filter should therefore never be washed completely.

You should also not clean it more than twice during the season so as not to endanger the biological balance inside. Maintenance of the pond filter also includes professional and timely winterisation to avoid frost damage to the system and pump.

Of course, you can also use a pond vacuum cleaner for cleaning. With this device, which works like a hoover, you can remove mud and algae from the bottom of the pond.

Teichfilter

To clean a pond filter, the pump must be switched off and the housing opened. Then remove the filter mats and rinse them with cold water.

Decision: What types of pond filters are there and which one is right for you?

There are different types of filters for ponds, which can be distinguished according to several criteria. Which filter you need depends on the type of pond you have or want to build.

Among other things, a different filter system will be of interest to you depending on the size (usually specified in litres of water), use (is it an ornamental pond or a swimming pond), shape/location (is there a slope or stream) and fish stocking.

Here we would like to introduce you to some forms of technical filter systems:

  • Pressure filter
  • Continuous flow filter
  • Underwater filter

In addition to these common types of filters, there are also the following less common ones:

  • Bead filter
  • Drum, fleece filter

How does a pressure filter work and what kind of pond is it suitable for?

If you have a small or medium-sized pond, a pressure filter might be suitable for you. These complete systems are very compact and have powerful pumps to build up high water pressure. This makes them ideal for feeding streams, fountains or waterfalls without the need for additional equipment.

So if you want to create a pond with a slope or fountain, the pressure filter is ideal. A pond pump transports the water into the filter, where it is cleaned. From there, it travels upwards against gravity in a hose and back into the pond basin via the stream or similar.

Advantages
  • Also suitable for small ponds
  • Can run streams and waterfalls
  • Can be buried below the water level
Disadvantages
  • Not automated
  • Filter material must be washed

Due to the high pressure in the system, it is also possible to bury the housing almost completely in the ground and hide it inconspicuously with covers. It is no problem if the filter is located a little further away.

What is a continuous flow filter and where is it used?

Continuous flow filters are a popular and widespread system that has proven itself for many garden ponds. They are probably the largest group of pond filters due to their ease of use and high performance.

They are versatile and suitable for all pond sizes as well as for ponds with fish. Another advantage is that continuous flow filters (except for the pond pumps) do not require electricity and are therefore energy-saving and less prone to defects.

Advantages
  • Suitable for all pond sizes
  • Very user-friendly
  • Energy-saving
Disadvantages
  • Not automated
  • Rather unsuitable for differences in height

Unlike the pressure filter, however, the water cannot overcome differences in height (without an additional pump). Brooks can therefore not be operated without further ado. If the device is used above the water level at the edge of the pond, a pump feeds the water into the filter, from where it runs back into the basin after cleaning.

The filter housing can also be installed hidden below the water surface so that no pump needs to be used. This system is then called a gravity or gravitation model.

Where can an underwater filter be used?

As the name suggests, underwater filters (unlike all other systems presented here, which are placed at the edge of the pond) work at the bottom of the pond in the middle of the pond. To set it up, all you have to do is place the filter in the pond and connect it to the electricity. Underwater filters belong to the mechanical cleaning systems.

Advantages
  • Small and space-saving
  • Hidden in the pond
  • Integrated water feature
Disadvantages
  • Not automated
  • Only for very small ponds

As this type of filter has a rather low flow rate, it can only be used in small ponds up to a maximum volume of 5000 litres. It is best suited for small ornamental ponds with no or few fish and can usually operate a water feature at the same time via the water outlet.

Unterwasserfilter

Underwater filters are placed at the bottom of the pond in the middle. It is suitable for small ornamental ponds.

How does a bead filter work and for which ponds is it used?

A bead filter is a special type of pressure filter. Inside the chamber is a large amount of tiny plastic beads, called beads. A bead filter is right for you if you want a particularly thorough biological water clarification, for example for your koi pond or swimming pond.

The beads offer a particularly large surface on which filter bacteria can settle well and form a biofilm. Very fine dirt particles also stick to them, which cleans the water. Due to the constant movement of the beads, the bacteria are supplied with sufficient oxygen and can also remove ammonia and nitrite from the water.

In addition to this biological filtration, the beads also have a mechanical effect: small contaminants get caught in the narrow gaps, only clear water can flow through. However, since coarser impurities such as leaves can quickly clog the filter, you should install a pre-filter. A sieve filter is suitable for this.

Advantages
  • Very good biological filtration
  • Easy to clean
  • Compact models
Disadvantages
  • Not automated
  • Prefilter is required

One advantage of the bead filter is that it is easy to clean. Usually the unit has a built-in function that swirls and rinses the beads extra vigorously; the detached dirt particles are removed from the filter through an outlet.

What is the difference between a drum filter and a fleece filter?

The biggest difference is the filter medium used. In the drum filter, the water (pumped or in a gravity system) runs through a drum made of stainless steel or plastic, whereby even very small dirt particles get stuck in the pores (which are only a few micrometres in size). In the fleece filter, the pond water is filtered through a roll of fleece or paper.

Both types of filter offer only mechanical water purification and therefore usually require an additional biological stage to break down pollutants dissolved in the water. Both enable a very fine-pored filtration of suspended particles.

Advantages
  • Automated systems
  • Very low maintenance
  • Hardly any electricity costs
Disadvantages
  • Very expensive to buy
  • Drum filter requires a sewer connection

Both drum and fleece filters are automated systems and therefore require relatively little maintenance. Both systems automatically detect the degree of contamination in the filter and initiate self-cleaning if necessary.

The drum filter requires electricity, as the drum rotates electronically to flush the screen. The fleece filter does not need electronics; it recognises when it is time to continue turning the fleece roll based on the increased water level in the filter.

Unlike the fleece filter, the drum filter should also have a sewer connection for wastewater drainage. Both drum and fleece filters are very expensive to purchase, but offer excellent, automated filter performance with low operating costs.

Buying criteria: Use these factors to compare and evaluate pond filters

Before you choose a pond filter for your planned or already constructed pond, you should consider a few things. To give you an overview, we will list the most important points here.

Basically, there are the following factors that play a role in the selection:

  • Pond size
  • Fish stocking
  • Pond type: natural, fish, swimming pond
  • Pond shape
  • Maintenance requirements
  • Maximum flow rate
  • Budget
  • Energy consumption

In the following section we will explain what exactly you should consider with regard to the individual criteria. After that it will be easier for you to choose the right filter.

Pond size

The most important decision point is definitely the size of the pond. Depending on how much water is in your pond, the filter must be able to circulate larger or smaller masses. If the filter is not strong enough for your pond, it will not be able to clarify the water sufficiently.

Pond size is actually a volume and is therefore expressed in cubic metres (m³) or litres (l). Here we show you how to quickly and easily calculate which filter you need. The rule of thumb is: length x width x depth x ½ litre

As an example: your oval pond is 5 m long at the longest point, 2 m wide at the widest point and 1 m deep at the deepest point. 5 x 2 x 1 x ½ = 5 Your pond volume is therefore 5 m³. To express this in litres, simply calculate your result x 1000, so 5 x 1000 = 5000l.

So choose a filter that is suitable for at least 5000l volume. For most models, this number is already given in the title ("Pontec flow-through filter MultiClear Set 5000"). The following table gives you a rough overview of which filter types are usually recommended for which pond size.

Type Pond size
Underwater filter up to 5,000 litres
Pressure filter up to 30,000 litres
Continuous flow filter up to 150,000 litres
Bead filter, drum filter, fleece filter from 150,000 litres

Fish stocking

If you have fish living in your pond, this will also affect your choice of filter, because fish place an additional burden on the water in the form of their waste production. The dirtier the water, the more efficient the filter must be.

We have calculated above that for a 5 m³ pond you need a filter with 5000 l filter volume. However, this figure changes with fish stocking. In general, you should multiply your result by 1.5 for a few, small fish. If you have many or larger fish, multiply by 2.

Teich

In the product description, the filter capacity for a fish pond is usually given as half that for a natural pond. The filter volume must therefore be twice as large. (Photo: derplani / pixabay.com)

Since the filter capacity for a fish pond only needs to be half as large as for a natural pond, you should choose a fish stocking filter, i.e. a filter with a capacity of 10,000 litres, for your pond measuring 5 x 2 x 1 metres.

Natural pond, fish pond, swimming pond

As already mentioned, the type of filter required is determined by the type of pond. There are very different ponds, ranging from small ornamental tubs and fish tanks to large swimming ponds.

Koi ponds are also a special case. Since koi are a sensitive and very large species of fish, a larger filter volume is necessary than for other fish ponds. Choosing a suitable filter is especially important when designing a koi garden. When reading the product description, you should therefore make sure that a suitability for koi ponds is mentioned.

For a small ornamental pool, an inexpensive underwater filter is often sufficient. For swimming ponds, for example, there are sophisticated systems with plants for decoration and simultaneous filtration. You should always consult a specialist dealer for more information.

Pond shape

Apart from the size of the pond, the shape of the pond can also change the demands on your filter. In particular, when buying a filter you should consider whether you would like to have a slope in your pond system, such as a stream or waterfall. Water features of various shapes and fountains cannot be operated with all types of filters.

If you want water to be pumped uphill in your pond, for example to flow back down a slope via a stream, a pressure filter would be best. This saves you having to buy and operate additional pumps.

Water features embellish the appearance of the pond and provide a supply of oxygen. They can be placed in the pond separately. More practical for small ponds, however, are certainly underwater filters with a built-in nozzle for a water feature.

Maintenance costs

You should also consider how much time and effort you are willing to invest in maintaining your filter. After commissioning, every filter needs to be serviced regularly. However, some systems are much easier to maintain than others. The difference in the maintenance effort is mainly due to the material used inside the filter.

Most commercially available pressure and flow filters use different types of filter sponges and mats. These become clogged over time and should therefore be removed from the filter and washed a few times per season to restore full performance.

In fleece filters, a fleece or paper roll is used as the filter medium. This can be easily replaced. A drum filter even cleans itself automatically.

If this work is too time-consuming or dirty for you, you should consider investing in a semi- or fully-automated system. Bead filters have a built-in cleaning function that makes cleaning easier.

Maximum flow rate

In the description of many pond filters you will come across an indication with the unit litres per hour (l/h). This refers to the so-called maximum flow rate of the filter and is usually between a few hundred and a few thousand litres.

The figure indicates how much pond water can be pumped through the filter per hour without damaging it. This is especially important when choosing which pump to use with your filter.

If the pump is too powerful, the pond filter may even burst. So be sure to match the pump's flow rate with the filter's maximum flow rate.

You may think that a higher flow rate is better because more water is moved in less time. However, this is not entirely true: if the water is moved too quickly, it will not stay inside the filter long enough to be cleaned effectively.

Budget

Another important consideration is, of course, price. Only you know what your budget is. You will certainly find a suitable pond filter in your price range.

A good filter does not necessarily have to be very expensive! Even for a small budget of less than 100 euros you can get underwater filters for ponds up to approx. 5 m³, which are powerful and often even have an integrated water feature. Pressure filter sets and some models of flow-through filters do not cost much more.

However, you will have to dig a little deeper into your pocket to purchase (semi-)automated systems. Drum and fleece filters as well as bead filters are very expensive at one to several thousand euros, but they offer more convenience in operation and excellent filter performance.

Energy consumption

In order to operate a filter, it must of course be connected to the power supply. The main energy consumption here is the pump, which transports the water either from the pond into the filter or from the filter back into the pond.

Most filters do not require any energy: the water flows through by gravity or by the pressure of the pump. The automatic cleaning system installed in the drum filter, on the other hand, needs electricity.

Solar panels are an alternative to laying a long power cable. Depending on their size, these can power only a small pump (3-5 watts) or a powerful pump and additionally also the UV-C device (up to 25 watts).

With the help of a rechargeable battery, the generated energy is stored, thus enabling filter operation even without sunlight. Of course, the solar system works best in a location with sufficient sunlight.

Facts worth knowing about pond filters

How can you build a pond filter yourself from a rain barrel?

Depending on the size of the pond, buckets, barrels or rain barrels can be used to build your own pond filter, whereby the filter volume is best chosen somewhat larger. Systems with one to four rain barrels, for example, have proven successful. These are filled with filter mats of varying fineness.

The barrels are built up in steps for optimal filtering effect and oxygen generation; this is easily done with elevations made of stone, pallets or similar. As with any multi-chamber filter, water is pumped from the pond and passed through the filter media via hoses. The location of the filter should be in the shade, if possible, to avoid algae growth.

What do you do with your filter in winter?

As soon as the water temperature drops below 10°C in late autumn or winter, the filter system becomes ineffective because the bacteria stop their activity. You should therefore winterise your filter system at the latest when it freezes permanently until next spring in order to avoid frost damage.

To do this, dismantle the filter as usual for maintenance and clean it thoroughly again; this time it can be cleaned completely. The pump must also be removed from the pond, cleaned and maintained according to instructions.

While you should store the filter and mats dry and protected from frost, the pump must be kept in a container with water. It is best to find a place for everything indoors, for example in the cellar.

How can you hide your filter?

To ensure that your filter does not disturb the surroundings around your pond, there are covers available from many manufacturers. These are available in various sizes and designs.

They are usually made of plastic with a stone or rock look, so that they can be well integrated into the vegetation. If your filter system is partially embedded in the ground, it is also a good idea to place a nice cover made of wooden slats over it. In addition, there is always the possibility of hiding the filter a little behind greenery.

Image source: Pixabay.com / Couleur

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