The Best Koi Pond Filtration System Setup

The filtration system is arguably one of the most important pieces of equipment that you buy when you have a koi pond. As most of you already know koi are notoriously messy fish and produce an awful lot of waste. Failing to provide the necessary means to remove the large amounts of solid waste and ammonia they produce is a recipe for a pond disaster.

Due to koi requiring very specific water conditions a lot of attention has to be paid to the ammonia, nitrate and PH levels of the pond among other conditions. A good koi pond filter system will help maintain these at the optimum levels ensuring perfect conditions for your fish to thrive.

In this guide we will be going over everything you need to know about choosing the best koi pond filtration system setup for your pond and what to look out for when buying.

Best Koi Pond Filtration System Setup

Does My Koi Pond Need A Filter?

The answer to this question is simply, yes! It doesn’t matter how big your pond is, as long as there are koi in there you are going to need a pond filter. Unfortunately, due to in-breeding Koi fish have a weakened immune system and are easily affected by changes in water quality.

In a pond there are numerous factors that can have an impact on water quality from fallen debris and uneaten food to decomposing plant matter and fish waste, there is plenty to keep on top of. A pond filter is by far the best way to combat the harmful excess levels of ammonia and nitrates that these factors produce.

koi pond filtration system setup

Choosing A Koi Pond Filter

Now that we have established the importance of having a filter installed in a koi pond it is also a good idea to understand what koi filtration actually is. In short koi filtration can be broken down in to two processes these are mechanical filtration and biological filtration.


Mechanical filtration refers to removing solid matter from the ponds water. Most notably we are talking about faeces, leaves, organic matter, uneaten food and the dreaded algae. This is best achieved through a multi-step filtration process consisting of multiple layers of mechanical media that are designed to catch debris of different sizes.

These multiple layers help to ensure as much debris as possible is removed from the water before it goes through the biological filtration process. This is highly important because if too much debris enters the biological part of your filter it can dramatically reduce the effectiveness of the nitryfying bacteria’s ability to convert the ammonia and nitrates in the water.

It is also important to remember that having the correct pump flow rate plays a vital role in the effectiveness of the mechanical filtration process. Having a flow rate that is too fast will lead to the water and more importantly debris passing through the filter before it gets chance to be removed.


Biological filtration is the process of using beneficial nitryfying bacteria to help detoxify and purify water. In a good koi pond filter there are a number of chambers with each containing a different media type. The media in each chamber provides a suitable home for the beneficial bacteria to survive.

There are many different types of media to choose from, but as a rule of thumb the bigger the surface area it has the better. A large surface area provides for better bio-filtration as there is more surface for the bacteria to colonise.

In addition to a large surface area the bacteria or biomass as it is also known as needs plenty of oxygen. This is why the mechanical filtration process is so important. If the mechanical filtration process isn’t working correctly then the biological media will eventually become blocked and ultimately starve the biomass of oxygen.

The best way to stop this from happening is be making sure there is adequate airflow reaching the biological media. This can be done with either an air pipe or the use of air stones under the media.

In summary both mechanical and biological filtration are essential for a healthy koi pond and this is something you should pay particular attention to when choosing a koi pond filter system. 

Pressurised Vs Non-Pressurised Filters

Pressurized Filters

pressurised koi pond filterPressurised filters are by far the most popular out of the two different types of filter available. This is mainly due the flexibility they offer when deciding where to install them. Due to them been pressurised you can install them at either ground level or below giving you far more options for concealing them.

It is definitely worth mentioning that water flows quite slow through a pressurised filter which has both its own advantages and disadvantages. In terms of filtration slow flowing water has the benefit of giving the mechanical media far more time to remove as much debris as possible from your pond water.

When it comes to biological filtration slow flowing water can have a negative impact on the beneficial bacteria in the biological media. This is due to nitryfying bacteria being aerobic and consequently needing plenty of oxygen to survive as well as process ammonia and nitrates. The problem with slow flowing water is that their is less dissolved oxygen which in some instances can be a problem..

Non-Pressurized Filtersnon pressurised koi pond filter system

The alternative to pressurised filters are non-pressurised pond filters which aren’t quite as versatile in terms of installation as their pressurised counterparts but offer superior biological filtration.

Also known as box filters they have the advantage of the water flow not been reduced up on entering the filter, which is a problem with many pressurised models. This is extremely good news for the beneficial bacteria within the bio-media as they will have plenty of oxygen to thrive.

Mechanical filtration is also very good with box filters due to the numerous layers of mechanical media they have. You can expect excellent results when it comes to the removal of debris.

If you have a heavily stocked koi pond this type of filter may be the best option due to the superior biological filtration they offer.

Choosing The Right Size Pond Filter and Pump For A Koi Pond

This is by far the most important thing to consider when choosing a koi pond filtration system setup and where many people go wrong. To make this as easy as possible to understand we have broke this crucial part of the buying process down in to bite size chunks for easy reading. There are 3 main points to consider when choosing a koi pond filter and they are all equally important for maintaining a healthy pond.

  • Pond Volume – The first thing to do is calculate the total volume of your pond. If you have a pond that is 2m x 2m and has a depth of 1m, the total volume would be 4 sqm. In every sqm of water there is a total of 1000 litres. So, 4 x 1000 = 4000 litres for the total volume of the pond.
  • Water Retention Time – It is recommended that pond water should be retained within the filter for 15 minutes for optimum results. The filter should also  turnover the entire volume of your pond evetry 2 hours or so. With our example pond of 4000 litres you would need a filter that is capable of filtering 250 litres every 15 minutes to achieve the recommended retention time.
  • Pond Turnover – Turnover refers to the time it takes for a filter to process the volume of your pond. With our example pond we would need pump with a flow rate of 2000 litres per hour to achieve the recommended turnover time.

The benefit of buying an all in one filtration system like the ones we have featured in our top list is that you don’t have to worry about choosing the correct pond pump as many already come with a pump that is capable of achieving the correct turnover time.

Best Koi Pond Filter System


All Pond Solutions Pressurised Koi Fish Pond Filter

All Pond Solutions Pressurised Koi Fish Pond Filter

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All Pond Solutions have one of the widest range of koi pond filters out of any brand and their models cater to ponds of all sizes. Offering the perfect mix of affordability and quality they are one of the leading suppliers of pond equipment in the UK.

The PFC-12000 is recommended for ponds with a volume up to 12,000 litres. However, for heavily stocked koi ponds you are talking more like 6000 litres and 9000 litres for medium stocked ponds.

With a built-in UV steriliser in every unit there is no need to worry about algae growth, harmful micro-organisms or parasites. The UV light will help to ensure optimum water quality for your fish pond or water garden.

The mechanical filtration consists of 5 different foams ranging from fine to coarse and designed to remove debris as small as 50 microns. Then water passes through tumbling K2 media significantly reducing harmful ammonia and nitrite from the water with the help of good bacteria. Bio balls with a large surface area are then utilised for the final stage of biological filtration.

What we really like about these filters is the easy maintenece. This is due to the cleaning handle which you simply turn to clean the foam media. This reduces the amount of times you will need to give the foam a thorough cleaning and is a deal clincher in my eyes.

Our View

Having both excellent mechanical and biological filtration properties and at a great price its easy to see why this is one of the best selling koi pond filters in the UK. Made by a brand that has a long history of supplying high quality pond equipment and with very positive feedback from previous buyers the All Pond Solution PFC range of filters come recommended by many.

All Pond Solutions Pressurised Koi Fish Pond Filter and UV Steriliser for PFC, 12000 Litre

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Fish Mate Pressurised UV & Bio Pond Filter

Fish Mate Pressurised UV & Bio Pond Filter

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Fish mate pond equipment is regarded as being some of the very best and we have to agree. There full range of products consistently receives excellent customer feedback and they are the choice brand for many fishkeepers.

The Fish Pond 15000 is one of their most popular models and it comes with everything you need for maintaining water quality and clarity. With a maximum flow rate of 7500 L/H it is suitable for ponds with a volume of 15000 litres.

Similar to the previous model it features an easy maintenence system that allows the filter to be cleaned with the simple turn of a knob. With this being an all in one koi pond filtration system there is of course a UV light and both mechanical and biological filtration. Unlike with some models the UV light is easy to replace not that you will have to do this often, but it is still a plus.

What some of you will really like about this filter system is the fact it can be installed above or below ground level giving you more choice when it comes to concealment.

Our View

Fish mate are undoubtedly one of the best pond filter brands and you pretty much can’t go wrong with any of their products. With a wealth of experience you can be certain that they know how to make a top quality koi pond filter system. This model comes with a 3 year guarantee which is also reassuring.

Fish Mate 15000 Pressurised Bio Pond Filter with Powerclenz

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All Pond Solutions PFC 50000 Koi Fish Pond Filter

All Pond Solutions PFC 50000 Koi Fish Pond Filter

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For those with the very largest of ponds that are heavily stocked with koi carp the PFC 50000 comes highly recommended. Suitable for heavily stocked koi ponds up to 30000 litres in volume and ponds with a mix of koi and other fish to 35000 litres in volume, it is a very popular all in one filter system.

The complete kit comes with the AquaEco 14,000 L/H pump providing continuous pressure helping to maintain water clarity. With this filter being designed for large ponds the UV-Clarifier is significantly more powerful than previous models featured in this guide helping to maintain ideal water clarity and quality.

In terms of filtration the mechanical process involves 7 different foams consisting of 3 fine and 4 coarse. Biological filtration is done with the use of K2 Media and bio balls. Both filtration methods are performed using the best media types for the top quality results making this our number 1 choice for big ponds.

As you may expect maintenence is reduced due to the use of the innovative cleaning handle. Simply turn the handle, open the outlet and let the dirty water out.

Our View

Maintaining a heavily stocked koi pond takes some handling and the PFC 50000 is more than capable of perfoming the task with relative ease. Every part of this filter is designed for maximum water quality and only the very best media types are used for the filtration process. The only drawback is the size and at 60 x 60 x 80 cm it is quite large but then that is to be expected considering it has a very impressive 170 litre filtering compartment.

Pressurised Koi Fish Pond Filter/UV Steriliser (PFC-50000-KIT)

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Oase BioSmart

Oase BioSmart

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The Oase BioSmart is a non-pressurised box filter that has been designed specifically for fish ponds. Customer reviews do the talking for this model as there is hardly a bad review to be found about it anywhere. We put this down to the almost unmatched filtration quality of the BioSmart and the very competitive prices.

With this been a complete filtration kit it has everything you need to achieve the best pond water possible. Included in the box is a Oase pump, filter and a built-in UV clarifier. Mechanical filtration is more than up to the standard needed for a koi pond and is achieved with multiple layers of mechanical media consisting of different porosity for maximum results. Optimised for bacteria colonisation and with a consistently high flow rate you can expect outstanding biological filtration with this pond filter.

Incredibly useful for the winter months in the UK is the built-in temperature gauge. Another positive is the light indicator that comes on when the media could do with a clean. Talking of cleaning the BioSmart features one of the best cleaning systems we have come across. All you have to do is take the lid off and raise the cleaning pads several times to remove built up debris from the foam media. The debris will then sink to be removed via the waste outlet. This cleaning system eliminates the need to remove the foam media and clean which is a hassle.

Our View

For medium to large ponds the Oase BioSmart is a top choice offering the very best in both mechanical and biological filtration. If you want the very optimum water conditions for your koi fish then this is the best koi pond filtration system setup for the job and a sound investment.

Oase BioSmart 14000 Set

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Koi Pond Filters – Commonly Asked Questions

Do I Need A Pre-Filter?


Final Words

The importance of owning the best koi pond filter you can afford should never be underestimated. With koi needing very specific conditions to thrive it is imperative that you do your duty as a fishkeeper and provide the best environment possible for both their benefit and your own enjoyment. A well maintained pond is a healthy pond and the pond filter system is undeniably a crucial factor for keeping a pond clean and healthy. Hopefully, you found this guide helpful and it included everything you didn’t know about choosing a koi pond filter system.

If you have any questions then drop us a message in the comments section and we will do our best to help you out.

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