Pond filter is an essential tool for effectively cleaning the water of any Koi pond. As you know, Koi fishes are a bit messy in nature, choosing the best Koi pond filter system becomes an obligatory requirement for you as a pond keeper.

Most often, koi fish shows a sensitive character during water changes. Your fish may get sick if the pond water isn’t clean enough to keep them healthy. This brings out the necessity of keeping the best pond filters for your Koi pond.

Koi Pond filter system basically performs their filtration task in two essential ways. They are the biological and mechanical filtration. Not different than regular aquarium filters, but of course with higher capacity. Besides, some pond filters also have a built-in or attachable UV filtration function that makes them more powerful than the traditional ones. More about that in a minute. But first let’s check out our top picks at a glance.

Our Top 3 Best Pond Filters for Koi

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What Should A Koi Pond Filter Must Perform

  • Biological filtration: The biological filtration system has a surface area which consists of a mass number of good bacteria that helps to eliminate all the harmful substances out of your koi pond. Subsequently, it turns ammonia into nitrite and then nitrite into nitrate which is less harmful for aquatic animals.
  • Mechanical filtration: You see, every fish pond is packed with different sizes of floating debris & wastes that make the water unhealthy for your fish. In that case, the mechanical phase collects and stores all these waste objects out of your pond and thoroughly cleans the pond water which is helpful for your koi fish.
  • UV Sterilization: The UV clarification system is a great purification process for purifying your koi pond from all kinds of invisible germs & microorganisms that cannot be cleaned easily by traditional filtration methods. The ultraviolet light inside the pond filter eliminates all those harmful objects and ensure the ultimate purification of your pond water.

Pressurized or Non-Pressurized?

Now, there are basically two kinds of Koi pond filter systems in terms of their mechanism & functionality. They are the pressurized and the non-pressurized pond filter. Let’s learn about both of them & find out the one which would be best-suited for you:

Pressurized filters:

Usually pressurized pond filters, also known as bead filter, provide superior filtration quality. The reason is the large surface area they offer through the biological filter media. More surface area means more room for the beneficial bacteria to thrive and perform better removal of ammonia and nitrite.

Another great feature of bead filter is the back-flush mechanism. It makes the cleaning process super simple without even touching the gunk.

Pressurized filters don’t depend on the gravitation force and as a result you may put it over the water surface or under it – your choice. May also bury it and hide behind anything.

Last but not least, you may install a UV sterilized with this. Most pressurized pond filters have built in UV function or options to add one easily.

Non-pressurized filters:

Non pressurized pond filters have non air tight lids. And most of them uses the gravity as their out flow function. There are positive sides of non pressurized filters as well.


First of all, you will need less capacity of pump to operate the pond filter than a pressurized filter to cover a same size pond. This will help you to save money from your pump budget.

As the filter media is easily visible and accessible it becomes easier to monitor and cleanup.

Non pressurized filters can provide more dissolved oxygen to the bacteria colony and during power outage they can survive longer in the filtration chamber than a pressurized filter. Also, non pressurized filtration system is easier to install than bead filter.

An innovative idea would be to use a non-pressurized filter as a pre-filter in front of a bead filter. By doing so you get the benefits of highly effective biological filtration system along with slow, high-volume mechanical filtration system in the bead filter.

Reviews of 5 Best Filters for Koi Pond

1. Goplus Pressure Bio Filter – Best Filter For Medium Sized Koi Pond

The Goplus Pressure Bio Filter is a powerful filter that can effortlessly purify any koi pond up to 1300 gallons of water (2600 gallons with normal fish load). It’s been powered by both bio-mechanical and UV clarification system which is designed to ensure the highest purification of your pond water. Not-to-mention, you will get one year of service warranty from the manufacturer.

Goplus Pressure Bio Filter has innovative dual outlet design that makes the cleaning super easy. As the name “Pressure Bio Filter”suggests a pressurized operation with greater efficiency. Let’s learn about all the features offered by this filter:


  • Suitable for small & mid-size ponds
  • Both Biological & Mechanical Filtration
  • Features Ultraviolet Clarification
  • Back-Flushing Cleaning Function
  • One Year Of Service Warranty


  • The lids are sometimes prone to leaks

2. OASE BioSmart 5000 – Overall Best Koi Pond Filter System

If you own a large size pond beside your home or garden, this can be the best filter for you. It comes with two size options and features both mechanical and biological filtration inside your Koi pond. You’ll get the option to add an additional UV clarifier with the filter. Let’s explore all the features offered by this particular:


  • Suitable for large & mid-size ponds
  • Both Biological & Mechanical Filtration
  • Built-in Cleaning indicator
  • Real-time water condition
  • High Surface Area with foams


  • Doesn’t come with a UV clarifier

Note: OASE Biosmart 10000 pond filter is from the same category as biosmart 5000 pond filter but with a larger capacity. If you need a filtration system with more capacity then go for the OASE Biosmart 10000 pond filter.

3. Aqua Ultraviolet A50007 Ultima II 6000 – Best Pressurized Filter For Koi Pond

The Aqua Ultraviolet is a pressurized filter which can efficiently clean all mid & large size ponds out there. If you’re looking for a powerful and efficient filtration system inside your koi pond, undoubtedly this would be the best filter option for you. The bio-mechanical filtration system along with an easy-to-clean feature makes the filter an ideal choice for all koi ponds. Let’s learn about all the features offered by this filter:


  • Capacity: This powerful pressurized filter can efficiently process up to 6000 gallons of water from your koi pond. If you own a large or mid-size koi pond, this filter is the real deal for you.
  • Core Functionality: The biofilm surface inside the filter prevents the bacterial growth from your koi pond and the good bacteria stored inside the components help to convert all the ammonia and toxins into harmless nitrates. Besides, the filter also has the ability to remove the same size debris in compare to other pressurized filters out there.
  • Cleaning: The filter features an easy-to-clean function that allows you to effortlessly clean all the components whenever it’s necessary.
  • Unique Features: The filter can be used as a standalone supplement to any small or large size koi ponds. However, although they are a bit expensive they are more optimized than other un-pressurized filters because of the powerful purification system they offer.


  • For ponds up to 6000 water gallons
  • Biofilm Surface Area
  • Bio-mechanical filtration
  • Easy-to-clean function
  • Standalone supplementary


  • A bit expensive than non-pressurized ones

4. OASE Gcp Filter Biotec Gravity 18000 – Best Gravity Fed Koi Pond Filter

This filter is manufactured specifically for large koi ponds that consist up to 18,000 gallons of water. Now, you can guess about its efficiency over cleaning out any beast size ponds. Besides, the filter also offers both biological and mechanical filtration for thoroughly purifying your koi pond. Let’s explore all the features offered by this filter:


  • Capacity: This filter can literally clean up to 18000 gallons of water koi pond that makes it suitable for all large size ponds.
  • Core Functionality: The filter offers both mechanical and biological filtration inside your koi pond. The water first goes through its mechanical filter and subsequently to the biological phase that separates all the debris & harmful substances out of your koi pond. The filter also has the ability to remove nitrogen compounds that are unnecessary and responsible to produce a mass number of algae inside your pond.
  • Cleaning: The filter is powered by a Screened Technology that prevents the filter from getting clogged by removing all the large size debris out of the filter. This makes the overall cleaning process more convenient for you.
  • Unique Features: The filter also has the feature to add a UV clarifier that can power up the overall cleaning process of your filter.


  • Best-suited for large size ponds
  • Both Biological & Mechanical Filtration
  • Function to add a UV clarifier
  • Screened Cleaning Technology
  • Prevents Algae Production


  • Doesn’t come with a UV clarifier

5. Grech CPF-2500 Pond Bio Pressure Filter – Best For Small Size Koi Pond

The Grech CPF has been made for all small size koi ponds for ensuring a powerful mechanical & biological filtration. The filter also comes with a UV clarifier that ensures the ultimate purification of your pond water. You’ll enjoy an easy-to-cleaning feature that’ll require less maintenance compared to other ones out there. Let’s explore all the features offered by this filter:


  • Capacity: If your pond has up to 900 gallons of water and a collection of Koi and other fish, this filter is no-doubt, an ideal option for you. Besides, if you only want to use the filter for decorative purpose, it can clean up to 1600 gallons of water from your koi pond
  • Core Functionality: The filter features both mechanical and biological filtration inside your Koi pond. Besides, it’s been powered by a UV clarifier that ensures the highest efficiency for cleaning your pond from all sorts of invisible toxins that could be a health concern for your fish. The biomechanical phase removes all sorts of bacteria and germs out of your pond water whereas the mechanical part holds all the large size debris and floating wastes from returning back to your pond.
  • Cleaning: The filter also comes with an easy-to-clean function that prevents you from frequently cleaning the filter and makes the cleaning process more convenient for you.
  • Accessories: The filter comes with adaptors for both inlet and outlet purposes.
  • Unique Features: This filter has the ability to adapt itself with both high and low water flow. Besides, it can be used to power a beautiful waterfall which is an added feature to your koi pond.


  • For ponds up to 900 gallons of water
  • Both Biological & Mechanical Filtration
  • Features Ultraviolet Clarification
  • Easy-to-clean function
  • Comes with adaptors


  • Not suited for large size koi ponds

How to Choose the Best Koi Pond Filter?

Best Koi Pond Filter

Now, you’ve got an extensive idea about the amazing features offered by five of the best koi pond filters in the market. You see, most of them offer quite the same cleaning functionality and some of them at least have the option to add more features. However, there are still some things to consider before choosing the perfect filter for your pond.

Let’s learn about all the crucial aspects you must know in order to get the perfect koi pond filter for you:

The capacity of your Koi Pond

Every koi pond filter system comes with a specific gallons capacity which denotes to its compatibility with a certain size pond. Some of them are only suitable for small size ponds while the other ones can handle ponds up to 20,000 gallons of water.

The rule of thumb is you need to circulate and pass the whole water volume of your pond through your filter in every 2 hours. So if you have a pond of 1000 gallons, you need a filter with at least the capacity of 500 gallons per hour filtration.

Pressurized or Non-pressurized filter?

As we’ve discussed earlier, the pressurized filters have more efficiency over the mechanical filtration system while the non-pressurized ones have more control over its biological phase. The decision of selecting one will mostly depend upon your pond as the first one takes a bit more time to carry out the cleaning task. This can be preferable if your pond doesn’t have a mass stock of fish.

On the other hand, non-pressurized ones provide more efficiency in terms of carrying out biological filtration. This is ideal for ponds with highly stock of fish. Finally, the last thing you should consider that the pressurized ones are a bit expensive than the non-pressurized ones. Whereas you can easily get the non-pressurized ones on a lesser price, but most of them don’t have the submersible feature inside it.

Compatible pump

No matter how efficient your koi pond filter is, you’ll need a pump with a sufficient GPH capacity to power up the overall cleaning process. Sometimes we buy a pump which has less GPH capacity than the filter. This may result in the inability of the filter to provide its potential performance and even blow up its internal components in case of the pressurized ones.

So it’s highly recommended for you to buy a pump with the appropriate GPH capacity that’ll enable your filter to deliver the potential performance inside your koi pond.

Cleaning function

Although koi pond filters don’t require frequent cleaning or maintenance, most of them come with an easy-to-clean feature. Some of them also offer a backwashing feature that only requires one or two-part movements to thoroughly remove the clogging out of your filter. So look whether one of the features are available inside the one you’re going to buy.


The price of your koi filter will mostly depend upon its capacity and type. If you’re going to buy a pressurized filter, the price may be a bit higher than the non-pressurized ones. On the other hand, you can get a non-pressurized filter within a less price than the “Bead ones” (Pressured filters are also known as bead filters).

In addition, the second most crucial factor regarding the price deficiency would be its capacity. As a rule, the filters having large capacity are a bit pricier than the small ones. So ultimately, the price will solely depend upon the size of your pond. For example, a standard 4000-gallon non-pressurized filter may cost you around $120 – $150 depending upon its performance & capacity.

Why It Is Important to Choose the Best Koi Pond Filters?

  • A good pond filter provides both mechanical & biological filtration that helps to efficiently clear out all sorts of wastes and harmful substances out of your koi pond. Besides, the process delivers the potential performance as per its specs.
  • Sometimes pond filters cannot purify large size ponds because of the limitations of it’s performance according to the capacity. But the best koi filters can effortlessly purify all size water ponds that are within it’s capacity.
  • They come with UV clarifiers or at least the option to add an extra compartment for storing ultraviolet lights to ensure the ultimate purification of your koi pond.
  • They have easy-to-clean backwashing feature that prevents them from clogging & allows you to effortlessly clear the stored wastes after a certain time.
  • They are compatible with most of the pond pumps out there & also have the ability to provide smooth performance in any water condition.
  • Some of them also come with helpful indicators that may notify you about the current water condition & also when it is the right time to clean up the filter.
  • Last of all, we know your Koi fishes are precious and expensive. To protect your precious friends you need the best gadgets in work.

How to set up a Koi pond filter?

Most of the pond filters come with an instructional manual for demonstrating you the appropriate way of installing it inside your pond. You can get the fundamental knowledge from that book. Besides, there are some general rules that apply for installing most of the pond filters out there. Let’s learn about them:

At first, you’ve to make a visual picture of the structure of your pond and all the available areas where you can appropriately install the whole function. Now, the function described here not only denotes the filter itself, but also the pump along with its necessary piping. It will be helpful for pumping the water to the filter & also continually run the whole process.

After drawing out the piping layout, determine the area where you can place the electric cord to power up the filter. Your cord needs weatherproofing before you will be using it on outdoor places.

Finally, make all the necessary electrical and piping connections between the pump & the filter. Start up the pump to see whether the whole process is running properly. That’s all, now you’re ready to go!

Frequently Asked Questions

What type of Koi pond filter should I buy?

As stated above, the type of filter you should buy will mostly depend upon the nature & denseness of your pond regarding the fish stock. Pressurized filters are best-suited for mechanical purification mostly. But they aren’t capable enough to handle ponds with a large stock of fish.

On the other hand, non-pressurized filters have more efficiency over biological filtration. If you own a koi pond with a high stock of fish, this particular category can be an ideal option for you.

How can I determine what capacity of pond filter & pump should I need?

The answer lies mostly upon the approximate size of your koi pond. Let’s say, if you own a 4000 gallons koi pond, you’ll need a pump that has at least 2000 GPH capacity or more.

The second most crucial info you must know is the pressurized filter needs a sufficiently capable pump to run its operation. This is because sometimes if the pump is not capable enough to push the required GPH of water inside the filter, it may cause the filter to even blow up because of the delay it has made while conducting the mechanical filtration.

Can I put my pond filter under water?

If you’ve gone through our list of koi pond filters, you’ll see the only pressurized filter we’ve reviewed has a submersible facility that allows you to put it under water. This gives you more flexibility over your pond side arrangements & beautification.

On the contrary, most of the non-pressurized filters aren’t submersible. You cannot place it fully under water unless it has that versatility feature. But there are some non-pressurized filters that do come with a submersible feature.

How often should I clean my Koi Pond filter?

You’ll need to clean it whenever it gets clogged by a large quantity of debris that significantly reduces the water flow. This means you will only need to clean the filter in case you notice a reduction in the water flow. Besides, it’s not good for the good living bacteria if the water flow is not fast enough.

Final words

Thanks for reading the whole post. We believe our guide has been helpful for you to get extensive knowledge about some of the best koi pond filters in the market. Besides, we have also provided you with a helpful buyer guide along with some essential know-how for making the overall “buying to installation” process effortless for you. Stay tuned with us for more info-guides like this. Thanks.

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