We adore our koi and always want the best for them, don’t we? But, unfortunately, they might make it difficult to love them. They’re the messiest eaters, and their biological output is, to put it mildly, tremendous.

Keeping your pond’s water clean regularly helps to keep the chemistry balanced and the ecosystem healthy.

Choosing the best filter for your koi pond may be a difficult task. To assist you, I’ll review everything you need to know about picking the best filter for your pond setup.

Best Koi Pond Filter

Now that we’ve covered the items to consider when selecting a filter, let’s have a look at my top picks for the best koi pond filter:

The Aqua Ultraviolet Ultima II 1000 Filter is the best little filter available.

The Aqua Ultraviolet Ultima II 1000 Filter is a small type ideal for koi ponds or aquariums ranging in size from 500 to 1000 gallons. It is modest and may be mostly hidden, so it will not interfere with the aesthetics of your pond. It pumps 500-1200 gallons per hour, depending on the size of your pond, swiftly cleaning it to keep your fish in the best possible conditions.

This device features one of the best koi pond filter media. It employs this company’s unique Ultima II filter series, which combines the advantages of mechanical and biological filtering in a tiny package. As a result, it has an extraordinarily high biofilm surface, promoting good bacteria development without smothering those healthy germs.

The mechanical filter employs a thick bed of ridged media that retains any particles that pass through the filter, avoiding clumping and allowing the water to flow freely without reintroducing those materials into the pond.

Another incentive to give this koi pond filter a go is the quick backwashing procedure. It employs a cyclonic approach in which you spin a valve to activate the internal jets within the filter. This removes the waste materials from the media and discharges them into the waste line. This process should only take a few minutes per week or so, depending on the purity of your water, so it shouldn’t interfere with your routine too much.


  • Small size
  • Quick backwashing
  • Media with a patent
  • What isn’t great about it? It works fine.


  • Expensive

TetraPond 26596 Waterfall Filter, 1000-Gallon Capacity

TetraPond 26596 Waterfall Filter, Up to 1000-Gallon
  • Quickly and easily creates beautiful waterfalls
  • Creates waterfall
  • Additional filtration

The size of this man was the first thing I noticed about it right out of the package. It was a pleasant surprise! The system combines a waterfall (aerating device) with a filter, a wonderful touch.

Designing usefulness into a gorgeous object is a stroke of genius. However, remember that the device is just a filter, so you’ll also need a pump and a UV light.

It’s a huge, heavy-duty plastic bucket with a strong lip for the waterfall. The installation is quick and simple, but a word of caution: the standard. A garden hose measuring 75 inches in length will not fit. To complete the circuit with the pond, you’ll need 1-inch or 1.25-inch tubing.

The fitting was also challenging, so take additional care while mounting the pump and checking for leaks. The intake is located at the back of the unit rather than the side.

Because the filter came with filter pads, mechanical filtering was excellent straight out of the box. Unfortunately, there were no plans for biological filtration. Lava rocks or bio-balls, whatever you like, must be purchased separately. This was annoying because it worked perfectly out of the box without a lengthy setup.

A quick request to Tetra: could you perhaps make the stickers easier to remove? The stickers on the sides of the filter were quite tough to remove and added nothing to the overall appearance. I realize it’s only an aesthetic issue, but it’s a little unappealing.


  • Simple, fundamental, and effective
  • Works right out of the package, and installation is simple.
  • Excellent value
  • When used as a water feature, it improves the pond’s appearance.
  • A waterfall can help with aeration.


  • Non-standard hose fitting that must be purchased separately
  • There was no biofilter material given, which appears to be an error.
  • The back inlet made piping in more difficult than it needed to be.

Grech CPF-2500 Pond Bio Pressure Filter UVC 13-Watt For Up To 1600 Gallons

SUN CPF-2500 Grech Pond Bio Pressure Filter, UVC Upto 1600 gal, 13W
  • Biological and mechanical filter chambers for more efficient removal of dissolved and solid waste
  • Simple quick handle cleaning system for easy maintenance (no need to open and clean foams all the time)
  • Enables rapid growth of aerobic bacteria resulting in removal of lethal ammonia and nitrite

Because it is the most recent generation filter, the CPF-2500 pond bio pressure filter should be the best choice for your koi pond. It is a high-performance bio-mechanical koi filter built using cutting-edge UV technology. This filter is appropriate for ponds with a fish load of up to 3,000 liters and without a fish load of up to 6000 liters.

This filter enhances water quality by maintaining a constant biological balance. Consequently, the water is crystal clear, and the koi pond residents live in a healthy environment.

This pressure pond filter features a UV device that combines biological and mechanical filtering to provide your koi pond with crystal clean water.

With the aid of UV light, the UVC clarifier in the filter can modify the protein structure of algae, obstructing its development.

Consequently, big clumps of algae accumulate, which can be readily removed from the koi pond water using mechanical pond filtration. Microorganisms build inside the filter during bio-mechanical cleaning and eradicate dangerous bacteria and germs from the water, producing a healthy habitat for koi pond occupants. Floating dirt and debris remain in the pond filter and do not return to the koi pond water due to the mechanical filtering process.

The filter has more effective mechanical and biological filter chambers that can readily remove dissolved and solid waste elements. In addition, the filter promotes the rapid development of aerobic bacteria, which is beneficial in removing hazardous ammonia and nitrite from the water.

The filter incorporates a simple, fast handle cleaning method, making it simple to maintain. This cleaning procedure is not necessary to open and clean the foams all of the time.

The filter may deliver more water than conventional standard gravity filters.

The filter should be placed in a shaded location with a temperature no more than 40°C.

Because direct sunlight raises the temperature, making it unsuitable for developing helpful microorganisms.

The filter features a small footprint and a simple cleaning mechanism to install and maintain. It does not need to be opened and cleaned with foam regularly in this instance. The filter also contains input and output tubing adapters, making it simple.


  • The most simple cleaning procedure
  • Biological and mechanical filters that are ready to use right out of the box
  • UV protection filter
  • It is simple to set up and maintain.
  • It is appropriate for ponds with a fish load of up to 3,000 liters and without a fish load of up to 6000 liters.
  • It generates clean water and fosters a healthy atmosphere.
  • It is the most recent generation of koi pond filter;
  • It is a simple bio-pressure pond filtration system.
  • It is capable of quickly removing both dissolved and solid trash.


  • Some users have reported leaks.

All-In-One Pond Filter System CNZ

CNZ® ALL IN ONE Pond Filter System with 13W Sterilizer 660GPH Pump Fountain Kits
  • Reduce algae, Clean Pond water
  • 3 Fountain Water Feature Attachments
  • Adjustment valve for regulating flow to fountain head and/or auxiliary water feature.

The CNZ product is an all-in-one in-water system with mechanical, biological, and UV functions. In addition, the built-in pump has a fountainhead adapter for decorative purposes and enhanced aeration.

This is an excellent filter for a small pond, a secondary filter in a bigger pond, or a series of ponds. It is simple to install; simply place the filtration system in the pond and turn it on. Nothing could be more straightforward. The equipment includes 15 meters of sealed cable to assist reach out to the most remote regions of a garden.

The best part is that you don’t need to buy a separate pump; it comes with an integrated UV lamp. This one does everything.

Because this filtration system is completely underwater, you won’t have to worry about concealing it or integrating it into the terrain. In addition to the huge foam filter, there are three filtering baskets where you may store your preferred filtering medium.

One of the finest aspects of this system is that it can also function as a water feature. It comes with three different fountain attachments and a splitter for creating a cascade to assist you in creating an eye-catching show.


  • The all-in-one device serves as a filter, a pump, and a UV lamp.
  • Filtration methods include biological, mechanical, and UV.
  • Excellent value for money
  • Pump built-in
  • Fountains and waterfalls may be created with this material.
  • There are three separate baskets for filter media included.


  • When full, the unit is difficult to raise out of the water.
  • Cleaning the foam filters is difficult without the capacity to backwash.
  • Cleaning may be challenging.
  • Replacement components are difficult to come by.

Pond Filter OASE BioSmart 5000

OASE BioSmart 5000 Pond Filter
  • Innovative Flow-Through filter design with biological and mechanical filtration provides maximum oxygenation.
  • BioSmart 5000 is suitable for ponds up to 5,000 gallons (with no fish).
  • High-surface area filter foams provide exceptional biological filtration capability.

This is the most costly and biggest capacity filter on our list. Because it is a stand-alone machine with a gravity-assisted feed out, it must be placed somewhat higher than the pool. However, it’s not little, so hiding will need some thinking.

These non-pressurized box filters were expressly developed with fish in mind. As a result, they provide some of the greatest mechanical and biological filtering we’ve seen in a low-cost koi filter.

The filtering system employs numerous layers of mechanical media with varying degrees of porosity, which aids in the capture of material of all sizes. This layered medium has been dual-optimized for bacteria colonization and serves as the filter’s primary source of biological filtration.

Although this is a novel design, the medium looks to be of great quality and well-tuned for vast quantities of bacteria to thrive quickly. The filters also have a high flow rate throughout, so low oxygen levels will not hamper bacteria growth.

Cleaning is simple. When the media gets clogged, a helpful light indicator will flash, and you can open the top of the box and physically lift the cleaning pads contained within each media form. This eliminates particles from the foam, which settles to the bottom and is discharged via a waste outlet after being done multiple times.

In addition, the filters contain a built-in temperature sensor, which is essential during the winter months when temperatures are near freezing, and a sludge drainage valve to remove the bottom muck that accumulates under the pads swiftly. They also come complete with a built-in 24-watt UV clarifier for free-swimming algae removal, which will also assist in eliminating dangerous germs that can create problems with weak and immature koi.


  • Volume Cleaning Ease
  • Excellent filtration
  • Temperature Indicator Cleaning Indicator


  • Poor instruction manual, with only arrows pointing to numerous unnamed sections.
  • Inadequately built outflow nozzle and fitting

Pond Pump And Filter Pennington Aquagarden Inpond 5 In 1

Pennington Aquagarden, Inpond 5 in 1 Pond & Water Pump, Filter, UV Clarifier, LED Spotlight and...
  • Instant solution for a clear and healthy pond: combined efficient pump and filtration package for ponds up to 600 gallons.
  • A comprehensive range of three fountain heads, fittings and adjusters included
  • The built in 5 watt UV clarifier light kills green water and algae

The final of my reviews is for Pennington’s in-water combo system. It’s another plug-and-play system that, like the others evaluated, exemplifies simplicity—five minutes out of the box, and it was in my pond and operating.

This is a filtration system designed for little ponds, but despite its modest size, it has a few tricks up its sleeve. Dual biological and mechanical filters provide versatility, and the UV option aids algae control. In addition, it contains a fountain with three different head attachments and an optional water feature.

Pennington’s unit also features an LED light, so you can add some glitz to your nights and show off your catch anytime your visitors come over.

It is simple to clean the filters. The unit’s compact size makes it simple to remove, clean, and replace parts as needed. One disadvantage is that there are two plugs, one for the UV and light and one for the pump. It’s not a major complaint, but having two outlets at the pond adds an unnecessary complication that might have been easily avoided.


  • Works straight out of the box
  • An LED light that is small, robust, and compact is an added plus.


  • Two outlets are required.
  • The fountain does not have a splitter for an additional water feature.

The Verdict on the Best Koi Pond Filter

I wanted to state from the start that there was a clear winner in our struggle for clean water, and I’m happy to announce that there is. The Grech CPF went above and above the call of duty. Furthermore, this device achieved so at an affordable price and with a 1600 GA rating—certainly no slouch in the size matters department.

The ease of installation, the fact that it is almost plug-and-play (assuming the connectivity difficulties are resolved), and the ease of cleaning makes this a victory in my book. In addition, Grech outperforms the less expensive Tetrapond by including UV and the biological substrate.

Considering the price, capacity, simplicity of use, and thoroughness, this is the greatest koi pond filter for the money. In addition, my koi pond’s water quality was excellent after two days—a must-have for any small to medium-sized koi pond.

Why Are Filters Important in Koi Ponds?

Koi are very filthy fish, as we all know. Bottom feeders by nature, koi love rummaging through the dirt and silt that collects at the bottom of even the most well-kept ponds. Even the greatest koi food does not always get consumed and ends at the bottom. On top of that, the fish add to the problem by excreting solid and ‘invisible’ waste.

At home, our filter must also deal with algae in the water since algae enjoy the bio-waste that koi create. We also have leaf fall and other things that wind up in the pond organically over time, adding to the fun. We’ve discovered that with koi being koi and in an outdoor pond, the filtration system is required and has a lot of work to perform.

Koi are descended from a tiny population of fish in Niigata, where breeding began in earnest in the 1700s. Koi were chosen and married based on their colors and patterns. The issue with this lack of diversification and inbreeding is that koi are less resilient than wild fish.

As a result, koi may suffer disproportionately from low water quality. While koi fish have a lengthy lifespan, poor water quality can shorten it. Therefore, the filter is the most critical aspect of your pond system for koi.

Can a Koi pond live without a filter?

A koi pond requires a filter because koi fish are filthy and emit a lot of waste, which can accumulate to dangerous levels. If you do not use a filter to clean the pool, the fish may not thrive.

Furthermore, algae and bacteria in the water and debris will gather at the bottom, making the environment unfavorable for koi fish. Therefore, the kind and size of the koi pond filter will be determined by the number of fish and the capacity of the pond, among other criteria.

As previously said, the filters are relatively reasonable. Therefore there is no reason not to have a koi pond filter in the fish habitat.

What To Look For When Purchasing A Koi Pond Filter

Let’s start with the basics: cost. Simply said, choose the greatest koi pond filtration system you can afford. You most likely have a budget for your pond, and I believe the filter will be the most important investment you make.

When it comes to filters, bigger is usually better for koi carp. This is because your koi will grow in their pond, and as they expand, so will their waste output. This must be accounted for year after year.

Aside from size, here are a few more aspects to think about:

Stages of Filtration

There are two steps in every koi pond filter: biological filtration and mechanical filtration. These two stages act in very different ways, yet both are critical to the health of your koi.

Filtration Methods: Mechanical vs. Biological

A mechanical filter mechanically separates particles from water using barriers, screens, beads, mats, or a combination of these materials. They may remove koi leaves, twig fragments, and bio-waste. Mechanical filters may also remove minuscule suspended particles that are fractions of a millimeter in size from water.

Mechanical filtration helps clean your ponds and restore their immaculate appearance. Of course, everyone in the neighborhood will be jealous of your crystal clear water. However, this isn’t the whole picture, and clear water isn’t always pure.

The second source of water health to examine is biological filtration. We’ve previously discussed how dirty koi are at the dinner table; now it’s time to discuss their restroom habits.

The bio-waste they generate is adored by many bugs, which is the source of the problem. Although you can’t see them, they significantly influence water quality and fish health.

Biological filters contain a variety of substrates that stimulate and enhance the development of beneficial microorganisms. When water runs over these bacteria, they feed on the ammonia in the water, turning it into the harmless Nitrate.

Many different substrates are available, but they all perform the same job.

The key goal is to have a big surface area for healthy bacteria to thrive on while yet allowing water to flow through the substrate.

ultraviolet (UV) filters

UV lamps are used to cluster the algae together. These bigger bulk are considerably simpler to detect and filter out than individual cells. Some filters and filtration systems include UV filters, whereas others require a separate system.

Both are effective, yet each has advantages and disadvantages. For example, a single until implies less cabling and connections, but a single unified unit may make it more difficult to reach, clean, or repair parts.

Filters that are pressurized or non-pressurized

You’ll also need to decide whether a pressurized or non-pressurized filter is ideal for your koi pond. Both systems have advantages and disadvantages.

Koi Filters Under Pressure (Bead Filters)

Pressurized koi filters, also known as bead filters, are particularly popular for koi ponds because they provide the most design versatility. Pressurized filters can digest large amounts of water and can be positioned at or below ground level.

Water flow is substantially slower with pressurized koi filters than through non-pressurized filters, which has numerous major ramifications.

Because the filtration media has more time to filter the water going through the system, the slow water movement results in greater overall filtration.

Beneficial bacteria, however, do not grow in slow-moving water because the oxygen they require to metabolize ammonia is depleted in this water.

Nonetheless, oxygen depletion is largely an issue in ponds with a high concentration of koi. Even so, you may improve biological filtration by including a pre-filter or an air bubbler in your filtration system or by adding activated carbon to your biological filtration medium.

  • Can be put above or below ground 
  • Capable of filtering extremely big water volumes 
  • Slow water velocity gives filtration more time to work
  • This leads to oxygen deprivation, which might severely influence biological filtration.

Koi Filters, Non-Pressurized (Box)

Box filters, also known as non-pressurized filters, are more straightforward to install than bead filters. However, because they have depth constraints and require a level bench to sit on, these submersible filters limit your pond’s design.

These filters have an advantage over bead filters in that they do not affect the flow rate of water from the filter pump. This implies that beneficial bacteria growing on the filter medium have access to lots of oxygen and may perform efficiently in busy koi ponds.

Even better, because the running water sweeps off dead bacteria, the greater flow rates of non-pressurized filtering systems allow the biological medium to clean itself. At the same time, the larger flow rate has no detrimental consequences on mechanical filtering.

While it is not essential in most ponds, a non-pressurized filter can be used as a pre-filter before a bead filter. As a result, you receive the benefits of both very efficient biological filtration and sluggish, high-volume mechanical filtration in the bead filter.

  • Simple to install
  • excellent biological filtration
  • less expensive than bead filters
  • self-cleaning biological medium.
  • imposes restrictions on pond design

The Pumping Station

The filter must be matched to the pump. If the pump has too much capacity, it may overflow the filter; if it has too little capacity, the filter will be ineffective, and your pond will get dirtier. A decent rule of thumb is to cycle the water in your pond every hour. A pump with a throughput rate of 1,000 GA per hour would be ideal for a 1,000 GA pond.

However, keep in mind that if the filter box is higher than the level of the pond, the pump will be pumping against gravity and will have to work harder. If this is the case with your system, consider adding more capacity.


Filters necessitate the use of pumps, and pumps necessitate electricity. Remember that all cabling must be weatherproofed and waterproofed (where necessary). Finally, consider the ease of access to the electrics during installation and maintenance.


The fundamental nature of filters implies that they will become clogged. Therefore, cleaning the filter regularly is part of your koi maintenance regimen. But, again, following the manufacturer’s directions is critical and avoiding taking shortcuts here.

To be honest, it’s not the most pleasant of activities; therefore, it’s well worth investing in a simple filter box or system to clean, disassemble, and replace parts. But, on the other hand, nothing is worse than putting off that unpleasant task for a day or two when it’s cold and wet since, in the end, the water quality will decrease.

How Much Filtration Is Required?

The quantity of filtration required for your koi pond is determined by two factors: the size of the pond and the number of fish in it.

Filters are graded according to the volume of water in your pond, so that’s where you should start. A pond containing koi fish, on the other hand, will require more filtering capacity than an empty pond because of the waste and crumbs these fish create.

As a general guideline, you should obtain a filtration system with two to four times the filtering capacity of your pond’s volume.

So, if you have a 1,000-gallon koi pond, you should acquire a filter that can handle at least 2,000 gallons. If your pond has a large number of koi or is exposed to direct sunlight for most of the day, use a filter rated for 4,000 gallons for that same 1,000-gallon pond.

Remember that this estimate offers a minimum filter capacity; if in question or between filter sizes, it is usually best to have more capacity than you require.

Should You Use a “Pre-Filter” to Improve Water Filtration?

Installing a pre-filter may be advantageous if you have a lot of detritus and a heavily stocked pond.

As previously mentioned, there may be advantages to pre-filtering water before it enters your main filtration system in some cases. This is more usual in well-populated koi ponds, but it may also work in smaller ponds if you want the optimum water quality. Pre-filtering is accomplished by placing a second filter device before your primary filter box. Skimmers, leaf baskets, or even a second filter box might be used to capture excess material or give additional bio-filtration.

Whether or not you need to pre-filter depends on your stock levels and filter selection since a decent non-pressurized box filter should be able to offer efficient bio and mechanical filtration for most koi pond sizes. However, if you have a lot of debris and a heavily stocked koi pond, installing both a bead filter and a box filter may provide the best filtration results.

If you opt to pre-filter using two filter boxes, ensure your pond pump is powerful enough to transport water between the two filter systems properly. Because just one filter will likely provide the primary mechanical filtration, some mechanical media from the bio-filter can be removed and replaced with extra biological media to improve bacteria colonization. This will also help maintain higher water pressure before reaching your main filter system.

Including Activated Carbon and Additional Beneficial Bacteria

In addition to a pre-filter, activated carbon and bacteria supplements can be used to improve water quality and promote bacterial growth. After installing a new filter, test the water in your pond once a month to see if your filtration system is up to the task. If you’re just experiencing minor increases in ammonia and nitrites, you may only need to add more beneficial bacteria to keep them at bay.

Similarly, adding activated carbon to the filter box every few months can help neutralize organic contaminants that bio-media cannot remove. Activated carbon can minimize the effects of chlorine, fragrances, pharmaceuticals, pesticides, fertilizers, and even stinky odors.

If your water quality tests show growing ammonia levels and your pond is quite clean, adding a pre-filter device (or second filter) may be the best option. In most circumstances, however, simply selecting a high-quality primary filter and supplementing it with bacteria and activated carbon is enough to maintain a pond in balance.

Maintaining Cleaning Routines

It is your filter’s responsibility to clean the pond, but it is also your responsibility to clean the filter. You will also need to skim off heavy material, like leaves and sticks, to protect your filter from becoming clogged.

The frequency with which you should skim your pond varies depending on what’s in it, but you should clean out the filter every 6 months.

Cleaning the Koi pond filter is typically simple because all that is required is to run clean water through it. However, if it doesn’t work, consider investing in replacement foam cushions. They’re reasonably cheap and will keep your filter running like new, keeping your Koi Fish alive and happy.


In the pet fish industry, there are several types of koi pond filters available. You should select the greatest koi pond filter to ensure that the water’s chemistry remains pure. Choosing the finest koi pond filter is one of the most critical aspects of koi pond maintenance.

As a result, we have compiled a list of the best koi pond filter, along with a review and buying advice to assist you in selecting the finest koi pond filter.

Last update on 2022-09-11 / Affiliate links / Images from Amazon Product Advertising API