5 Best Koi Pond Filters – Healthy Environment for Your Fish

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Last updatedLast updated: January 30, 2021
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A koi pond can be a beautiful and relaxing addition to your backyard. Of course, you need to keep the water clean for the fish to survive. This means adding the best koi pond filter to your other accessories. These units get rid of the waste, bacteria, and other debris for the healthiest environment possible for your fish to live in.

There are several different filter models on the market to choose from. We’ve reviewed five options, with the Goplus Pressure Bio Filter 4000GAL coming out on top. It is great for ponds up to 2500 gallons, has a flow rate of 4000 gallons per hour, and a 25-liter capacity. This pressure filter is fully assembled, easy to install, and has a decent price for added convenience. There are also a few others in our reviews for different pond sizes if needed.

When choosing a new filter, there are a few features to look at. One is the pond size, so you know the filter can handle the amount of water and fish in there. There are few different filtration systems, each of which covers a different cleaning aspect, so check these out as well. The size of the outlet matters since these affect the flow rate of the water. The unit’s dimensions tell you how much space it takes up and the warranty covers you for any issues with the filter. To help you choose the best koi pond filter, we’ve created a comparison table with in-depth reviews and a buying guide at the end to cover every feature.

Top 5 Koi Pond Filters Review 2021


Goplus Pressure Bio Filter 4000GALEditor’s Choice

  • Pond size: 1.500 (normal fish) or 2.500 (heavy fish) gallons
  • Filtration stages: Biological, mechanical, UV
  • Pressurized: yes
  • Outlet size: 3/4”, 1”, 1 1/4”, 1 1/2”
  • Dimensions: 14,96” x 14.96” x 20.07”
  • Weight: 17.74 lbs
  • Warranty: not specified

More features:  Built-In UV bulbs system

If you’re looking for the best koi pond filter system for your outdoor pond, the Goplus Pressure Bio Filter 4000GAL may be the one for you. It is perfect for new ponds or ponds you’ve had for years, clearing out the moss, algae, and other debris quickly for clear water your fish can enjoy.

This filtration system is perfect for normal fish ponds up to 1500 gallons or larger ones with 2500 gallons of water for a heavier fish load. It has a large capacity of 25 liters, with a flow rate of up to 4000 GPH.

The Goplus model is a pressure filter with 3 filtration stages built into one unit. First is the mechanical filtration stage, which gets rid of the solid wastes produced by the fish, as well as any pollen, decaying plant materials, and so much more. The biological filter keeps the beneficial bacteria at safe levels, adding oxygen to the water at the same time.

There is also a UV filter in this unit, which kills any viruses, algae, and mold that could be lurking in your water. Together, these three filters keep your koi pond clean and clear for healthier, happier fish.

Though the instructions included with this filter aren’t very clear, the unit comes fully assembled for quick installation. There is a backflush system, plus it is pretty simple to take the unit apart to clean it out whenever needed.

What we liked:

  • Fully assembled
  • Easy set-up
  • Decent price
  • Fast cleaning

What could be better:

  • Limited instructions

Aqua Ultraviolet Ultima II 1000 FilterBest Small Filter

  • Pond size: 500 to 000 gallons
  • Filtration stages: Biological and mechanical
  • Pressurized: yes
  • Outlet size: 1.5” or 2”
  • Dimensions: 14” x 23 1/4”
  • Weight: 23.2 lbs
  • Warranty: 1 year

More features:  Top valve mount, Aqua UV tubular media, pre-seeded with natural bacteria

The Aqua Ultraviolet Ultima II 1000 Filter is a compact model that is perfect for koi ponds or aquariums that range from 500 to 1000 gallons. As well as being small, it can also be mostly buried, so it won’t disrupt the aesthetics of your pond. It pumps 500-1200 gallons per hour, depending on the size of your pond, cleaning it quickly to keep your fish in the best environment possible.

This unit has one of the best filter media for a koi pond. It uses this brand’s patented Ultima II filter series, which combines the benefits of both mechanical and biological filtration in a small unit. It has an extremely high biofilm surface, which encourages beneficial bacteria growth without suffocating those healthy microbes.

The mechanical filter uses a thick bed of ridged media, which traps any of the solids that pass through the filter, preventing clumping so the water can flow freely without releasing those solids back into the pond.

Another reason to try out this koi pond filter is the simple backwashing process. It uses a cyclonic method, which requires you to simply rotate a valve to activate the internal jets inside the filter. This separates those collected waste materials from the media and shoots them out through the waste line. This process only takes a few minutes each week or so, depending on the cleanliness of your water, so it shouldn’t be too disruptive to your schedule.

What we liked:

  • Compact size
  • Fast backwashing
  • Patented media
  • Works well

What could be better:

  • Expensive

Aquascape 95053 UltraKleanBest Warranty

  • Pond size: 2.000 gallons
  • Filtration stages: Biological, mechanical, UV
  • Pressurized: yes
  • Outlet size: 1″, 1.25″, 1.5″
  • Dimensions: 13” x 17”
  • Weight: 12 lbs
  • Warranty: 3 years

More features:  Bulb-saver timer

Even the best pond filter for koi can have its issues, which is why you need a decent warranty to cover it in case those issues keep it from working at its optimal level. This one is covered for three years, so any repairs or replacements won’t cost you a thing during that time.

Of course, a filter is more than just its warranty, which the Aquascape 95053 UltraKlean has proven. This unit has a unique sponge-free design, which reduces maintenance while giving you the most efficient filtration possible.

The UltraKlean has three filtration stages. The mechanical filtration uses a water inlet diffuser, which evenly distributes the debris, reducing clumps. There are UltraKlean BioBalls inside that help trap the dirt and debris, plus helps with the biological filtration for producing beneficial bacteria.

A UV clarifier is the third stage of this filtration system. It eliminates the single-celled algae that turn the water in your koi pond green. This uses a UV light, which can burn out if used too much. To prevent this, there is a bulb-saver feature that allows you to set the UV to turn on at specific times.

Another great feature is the cleaning indicator light, which notifies you when the filter needs to be backwashed. This process is quite easy, using the valve to redirect the water and stir up the media inside. This flushes out the debris in only minutes, so it won’t take up a great deal of your time.

What we liked:

  • Indicator lights
  • UV bulb saver
  • Sponge-free design
  • Five-minute backwashing

What could be better:

  • Not for cold weather use
  • Pond size: 1.000 gallons, 500 gallons – maximum for koi pond
  • Filtration stages: Biological, mechanical, UV
  • Pressurized: yes
  • Outlet size: 1/2″, 3/4″, 1″
  • Dimensions: 12” x 17”
  • Weight: 9.1 lbs
  • Warranty: 2 years

More features: Backwash facility, cleaning indicator and a UVC viewing window

If you’re on a budget, you likely can’t afford to spend hundreds of dollars on a koi pond filter. The Jebao CF-10 Pressured Pond Bio Filter is a good solution, costing less than a hundred dollars while still keeping your koi pond clean and your fish healthy.

This filter system uses 3 stages of filtration to clear out everything that doesn’t belong in your koi pond. The mechanical filtration also has three stages of its own, including coarse, medium-coarse, and fine filtration. There are specific foam sponges used for each one to remove different sizes of debris from the water.

The biological filtration uses bio-balls, which encourage the growth of healthy bacteria that can fertilize the aquatic plants in your pond and create a healthy environment for your fish.

The third stage is the UV filtration, which uses a low-voltage UV light. As the water passes through this filter, the UV light kills any algae in it before it is sent through the output and back into your pond.

Cleaning this unit is easy, using the integrated backflushing system. This takes only a few minutes every week or two, depending on the condition of your water. The material used for this unit is thin plastic, so you do need to be a bit gentle with it. Keeping it out of direct sunlight helps maintain the plastic’s integrity. It is also recommended to place it in a hole to secure its position next to your koi pond.

What we liked:

  • Low price
  • Cleaning indicator
  • Simple installation
  • Easy to clean

What could be better:

  • Thin plastic

OASE BioSmart 10000 Pond FilterCustomer’s Choice

  • Pond size: 5000 to 000 gallons, 2.500 gallons – maximum for koi pond
  • Filtration stages: Biological and mechanical
  • Pressurized: no
  • Outlet size: 2.5”
  • Dimensions: 30” x 22” x 16”
  • Weight: 31.6 lbs
  • Warranty: 3 years

More features:  Innovative Flow-Through filter design, built-in cleaning indicator, water temperature display

If you have a large pond that is need of a decent filtration system, the OASE BioSmart 10000 Pond Filter may have the best koi pond filter design to meet your needs. This unit is rather large, so it may be hard to disguise with other pond features, but it is capable of cleaning a pond up to 2500 gallons for a koi pond or a 10,000-gallon pond without fish.

The BioSmart uses a unique flow-through design, which uses both biological and mechanical filtration systems to clean the water and provide the maximum oxygenation possible. It includes filter foams with a high surface area that offer excellent biological filtration. There are distinct filter zones to help promote the growth of beneficial bacteria, which helps maintain the proper nitrogen cycle for reducing harmful ammonia in the pond.

There are also some handy features included for easy use. The first is a built-in cleaning indicator, which tells you when to clean the filter. This process is simple since you don’t even have to take out the filter foams or manually unclog them. You can also open the sludge drain to easily remove any coarse debris.

Another unique feature is the water temperature display, so you always know the exact temperature of the water in the pond. You can pair this with a pond pump and UV clarifier as well, though they are not included with the filter system.

What we liked:

  • Cleaning indicator
  • Water temperature display
  • Sludge drain
  • Easy to clean

What could be better:

  • Limited directions
  • Large size

Things to Consider

Koi will spend their entire lives in the pond you build for them. This includes eating, sleeping, and using the figurative toilet. They also create a lot of waste, which then needs to be cleaned out of the pond for them to live comfortably. This means getting the best koi pond filter system to clean out the debris, waste, and reduce harmful bacteria that could create an unhealthy environment for your koi.

Features to consider while choosing a koi pond filter?

When looking for a new koi pond filter, you’ll likely notice a list of features that you may not be familiar with. The following sections will help you learn what each of these features is and why they are important for your new filter system.

Pond size

5 Best Koi Pond Filters - Healthy Environment for Your Fish

When looking at the pond size recommended by the pond filter you’re considering, there are a few factors you need to add. An empty pond will stay cleaner than a pond with fish in it, so the recommended pond size varies for these two instances. For instance, the OASE BioSmart 10000 Pond Filter has a recommended pond size of 5000 to 10000 gallons, though only 2500 gallons for a pond that contains koi. If the listed pond size is vaguer, you should double the size of the filter for the pond. For instance, the Aquascape 95053 UltraKlean has a recommended size of 2000 gallons, so it should be used on a 1000 gallon pond that contains a decent amount of koi. You also need to take into account the amount of fish.

A larger fish population requires a larger pond filter to keep up with the waste produced.

Filtration stages

There are two main filtration stages for koi pond filters. The first is the mechanical filtration, which removes the solid waste and other debris from the water that flows through the unit. This filter system may include different types of foam filters to catch varying sizes of debris.

There is also biological filtration included in the best koi pond filters. These capture bacteria, such as ammonia, and help it detoxify and become beneficial bacteria that actually improve the environment of your koi pond.

Some units also include UV filtration, which isn’t the same as the other filtration types. UV filtration uses a UV bulb that destroys the DNA of the free-flowing algae in the water, killing the algae. This causes the damaged algae to clump together, making it easier to remove from the pond.

Outlet size

The outlet size on the pond filter affects the flow rate of the water as it passes through the unit. The flow rate determines how quickly the pond is cleaned, so this is quite important. To choose tubing for the pump and any water features, you need the proper outlet size to move every drop of water through the filter each hour. The larger the outlet, the larger the tube size you can use, so the stronger the pump can be to push the water through at the optimal level.


5 Best Koi Pond Filters - Healthy Environment for Your Fish

The dimensions of the unit determine how much space it will take up next to your koi pond. A larger unit, like the OASE BioSmart 10000 Pond Filter, will be difficult to hide with decorative features around your pond. This can be a bit unsightly, though necessary for a clean koi pond. Some units can be hidden by burying them almost entirely next to your pond.


It’s best to check out the warranty of a pond filter before you buy one to ensure it covers any issue you may discover when you set up the filter and start it up. The longer the unit is covered, the more time you have to work out those kinks. Some warranties are only for a year or two but a few options, like the Aquascape 95053 UltraKlean, have a full 3-year warranty, so you can try out the unit to make sure it works as expected.

Extra features

5 Best Koi Pond Filters - Healthy Environment for Your Fish

There are a few extra features you may want to check out before buying a new koi pond filter system. One is the materials used to make the unit. All the products we’ve reviewed are made of plastic, so likely can’t be used year-round. This also means they may not be as durable as some other materials, so be careful with your filter.

Cleaning is another thing to look at. The easier it is, the more enjoyment you’ll get out of your koi pond. A backflush option is best since it cleans the unit itself rather than you taking it apart to clean it. This also only takes a few minutes, which is much less time than manually cleaning it out.

How to pick the right pump for koi pond filter?

When choosing the right pump for your koi pond filter, you need to look at the size of the koi pond. The unit should filter all the water in the pond every hour, so the pump needs to be able to cover this. For instance, if you’re pond holds 5000 gallons of water, the pump needs to have a flow rate of at least 5000 gallons per hour. Though a non-pressurized filter won’t interfere with this, a pressurized one will reduce the flow rate as the water goes through it. If the pump is too strong, it can damage the pressurized filter, so check out the filter’s pump requirements before hooking one up.

How to set up a koi pond filter system?

Setting up a koi pond filter system is easier than you may think. The following tips will get you started:

  • Determine the layout of your pond, including the piping for the pump and the filter
  • Install the pipes for the pump and the filter, creating a closed-loop system that goes from the pump to the filter and back into the pond
  • Install any electrical equipment, including wiring and circuit breakers
  • Set up the pump and filter, using the proper connections to give you the proper flow rate
  • Choose the proper pump and filter for the size of the pond and amount of fish in it


The price of your new koi pond filter may be a deciding factor on whether or not you buy it. Many of the products in our koi pond filter reviews are a few hundred dollars, which can be a bit pricey for those on a budget. There are a few that are budget-friendly, though, such as the Jebao CF-10 Pressured Pond Bio Filter. These units still have most of the features found on the more expensive models, though they may skimp a bit here and there. This doesn’t mean they won’t still do the same job, though. They are still fine filters, keeping your koi pond clean and your fish happy.


This depends on the cleanliness of the water in your pond. If the pond starts quite dirty, you’ll need to clean the filter more frequently to keep the water flowing through it smoothly. Some models use a backwashing function, which takes only a few minutes to clean out the unit, even if you’re running it every week. Non-pressurized filters need to be cleaned manually, so keep an eye on water flow. If it slows down, it’s time to clean it out.

A pre-filter is a second filter device that is placed before the main filter. It collects extra debris and adds some more bio-filtration, keeping this debris out of the main filter system. Though they can be beneficial for a larger pond that’s heavily stocked with koi or other fish, they aren’t necessary for smaller ponds with only a few fish. They also require a stronger pump since it’s going to need to push the water through two filter systems instead of one.

Yes, a koi pond filter is safe for water plants. The filter will circulate the water in the pond, which helps increase oxygenation. Since plants and fish both need oxygen, this benefits both of them. The movement created by the filter will also improve the plant’s ability to trap sediment and absorb the nutrients in the water, which helps them grow. Plants in the pond even keep the water clean, so the filter doesn’t have to work as hard.

Our Verdict

There are several koi pond filters on the market, so it may be hard to choose the right one to meet the needs of your favorite fish. We do have a few favorites that we think deserve a second look.

Our top choice and the best koi pond filter is the Goplus Pressure Bio Filter 4000GAL. This pressure filter can handle up to a 2500-gallon pond, has a 25-liter capacity, and a 4000 GPH flow rate. It comes fully assembled, so it easy to set up, and includes a backflush system for fast cleaning.

The Aqua Ultraviolet Ultima II 1000 Filter is best for smaller koi ponds due to its compact size. It uses both mechanical and biological filters and comes pre-seeded with natural bacteria for healthy growth. The cyclonic backwash method cleans it in only minutes.

The Aquascape 95053 UltraKlean uses three-stage filtration, with a sponge-free design that reduces maintenance time. It also includes a bulb-saver timer for the UV clarifier and has a cleaning indicator light to tell you exactly when to clean the unit.

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