Selecting the right filter for your pond is an essential part of long-term ownership and care. There are many pond filtration options to choose from, and by using this guide and our product recommendations, you’ll find it easy to pick the right one.
To help you arrive at the best decision, we’ve compiled essential information and given our recommendations on the 10 types of pond filters and filtration systems. But first, let’s talk about the two most common pond filtration systems.
Mechanical and biological pond filtration systems
Filtration is a requirement in pond management, to remove waste like ammonia and to create a naturally-balanced environment. However, not all filters achieve this in the same way.
Mechanical and biological are the two most common general types of pond filtration systems. Mechanical filters work by trapping and getting rid of debris and sediment. Examples of mechanical filtration media include filter brushes, sponges, and vortices.
Mechanical filtration
Physically separates any solids or waste from the water. While it may look clean, it does not remove toxic substances like ammonia, dissolved in the water.
Biological filtration
The use of beneficial (nitrifying) bacteria detoxifies and purifies the water column. Filter media materials provide living space for bacteria to grow while removing toxins.
On the other hand, biological filters break down pond waste and convert it into less harmful compounds that can be utilized as aquatic plant fertilizer. Filter mats, bio balls, and brushes are examples of biological filter media.
Most filter systems for ponds include a combination of both biological and mechanical filters, since aeration is a key part of keeping a healthy pond environment. Chemical filtration and the use of UV pond filters and or water clarifiers have too many disadvantages and are generally not not recommended.
Top Filters And Filtration Systems For Ponds
Now, we can move on to our top recommendations for filters to use in small ponds, large ponds, and koi ponds. We will also explain why our research led us to these choices based on their price range, maintenance needs, user experience, functionality, and overall value.
1. All-in-One Pond Filters
All-in-one filters handle the mechanical pump and filtration together in one kit. They are available in varying sizes, so make sure you read the manufacturer’s label to ensure your filter is the right size for your pond and fish load.The market has a few compact all-in-one submersible pond filter systems. They integrate UV clarifiers, pumps, and filter media.
Best for: Small fish loads, or ponds with less than 1,300 gallons. They also work for large ponds that need more filtration added.
Pros and cons: Easy to install and many include a maintenance handle for removal from the water. Entry-level product and low experience necessary.
Classification: Mechanical and biological systems.
Nualgi’s All-in-One Pond Filter Recommendation:
Lifegard Aquatics All-in-One Pond Equipment Triple
- From $277.69
- Completely submersible unit
- 2-stage high capacity mechanical filtration (2 types of sponges) to remove solids
- Biological filter for bacteria growth
- 13-watt ultraviolet sterilizer with separate 20′ cord to be used only as needed
- Quiet and efficient
2. External Pressurized Filters
These sealed plastic tank filters work as a gravity-fed filtering systems where the water flows downhill to the pond. They can also work to send the pressurized water up a slope or hill. You may want to conceal this external filters with landscaping and other features, to create a better aesthetic.
Easily hidden and also serve as an efficient filtration unit to boost your current system!
Water can be pumped over the pond edge or through the side of the pond to the filter if it is used with a submersible pump. The filter can be a long distance away and located either above or below the water surface. For heavy solid loads, use an external pump to draw from a vortex pre-filter that is gravity-fed from a bottom drain. More typically, you’ll find the external pump will draw from a slotted pipe intake.
Best for: Larger ponds of up to 60,000 gallons or a high fish load.
Pros and cons: Quick and effective backwash feature cleans without the need to open the canister and get your hands dirty. It can potentially clog, which will lead to a slow flow rate. Not always recommended for beginners due to the tubing setup, head pressure, and flow rate management.
Classification: Biological but can be combined with other filters and pumps to create a larger filtration system.
Nualgi’s External Pressurized Filter Recommendation:
- From $265.35
- 4000GAL pond pressure bio filter
- Easy, uncomplicated
- The effective bio-pressure pond filter system
- Includes a built-in 13-watt UV-C light / UV bulbs system
- Easy to maintain
- Comes with all parts ready to install
3. Bead Filters
Bead filters clean water by pumping it through a plastic chamber with floating bead balls. Inside the chamber, bacteria is grown and particles are removed out of the water. The bacteria within the beads keep the water naturally clean.
The captured solids accumulate inside the filter to remove dirt and water-clouding materials out of the pond. This requires significant amounts of cleaning since the debris may not sink to the bottom of the pond. The filter also cannot collect larger debris like trash and stones.
Backwashes are required for most bead filters. This means they need extra maintenance, plumbing, can be an eyesore, and many can’t backwash with just water.
This filter will also not collect larger debris like trash and stones!
Best for: Medium and large high-density fish ponds; mostly up to 10,000 gallons.
Pros and cons: May require loud air blowers for the backwash feature. It can potentially clog and slow the flow rate. Bead filters need extra maintenance. Not recommended for beginners due to the tubing setup, head pressure, and flow rate management.
Classification: Combination of biological and mechanical as both mechanical filtration and biological filtration take place in bead filters.
Nualgi’s Bead Filter Recommendation:
Aqua Ultraviolet Ultima II 6,000 Bead Filter
- $1,488.46
- Takes only minutes to backwash
- With a very high flow rate
- Max pump flow rate of 6,000 GPH
- One of the best tools for koi ponds or heavy fish loads
4. Skimmer Box Filters
A pond skimmer’s primary function is to get rid of debris falling into the water. It has a pump inside that draws in water to the skimmer, then the ‘weir’ – which is essentially an external door to the filter – produces surface tension that keeps the water flowing smoothly into the skimmer. Without a skimmer, your pump can get clogged or damaged by leaves, sticks and other debris sinking to the bottom of the pond.
Skimmers come with nets and baskets for catching all sorts of debris!
So, when you need extra assistance with removing leaves because your pond is under trees, you can add on a skimmer box to take your filtration to the next level. If you have a high-volume pump, a compatible skimmer filter will support it nicely.
Skimmers come with nets and baskets for catching all sorts of debris. Be sure to manually remove the skimmed materials from the filter often to maintain the flow. You’ll also need to maintain the skimmer brush and the gatekeepers.
Best for Any size pond. Useful with high volume pumps and removing large quantities of pond debris from trees or landscaping.
Pros and cons: Easy to lift out skimmer net for fast and easy maintenance. Can be complicated to install since you need to match the flow rate of hoses, pump, adapters, and head pressure.
Classification: Basically mechanical as it works to rid the water of all types of debris or foreign matter.
Nualgi’s Skimmer Filter Recommendation:
- $176.12
- Surface skimmer and filter with a rugged construction
- Designed for fast and easy maintenance with a lift-out skimmer net
- Can create custom configurations with the large media/pump chamber
- Weir door design regulates water intake to the pump chamber
5. Waterfall Filter Boxes
Waterfall filters are molded plastic tanks filled with filter media that both filter water and function as the headwaters of a waterfall. They are generally placed on the edge of the pond with wide flat rocks to conceal the waterfall, and force water to flow over the rocks.
Surrounded by soil from the pond or dug into a hillside, waterfall filters add extra elegance, filtration, and oxygenation to your pond. We highly recommend this filtration option for both its aesthetic and functional value. Larger models can handle up to 10,000+ gallon pond sizes and have a maximum pump flow rate of 20,000 GPH. Most have a 2,000-GPH flow rate and work for 3,000-gallon pond sizes.
Use the media bag and filter pads to remove excess organic materials, and include include bio balls in the media bag for increased water filtration capability. This maximizes the surface area for bacteria. This kind of filter works best in a pond with a low biological load, and can also be used to increase filtration in fish ponds.
Highly recommend this filtration option for both its aesthetic and functional value!
Best for: Any size pond with low biological loads, or to increase filtration in fish ponds.
Pros and cons: Filter pad or media can be removed and cleaned. Waterfalls can grow string algae that has to be removed manually. Can be costly due to pump, pipes, and installation fees.
Classification: Basically biological as water flows through filter mats and into bio-media chambers to offer a great addition to your current filtration system.
Nualgi’s Waterfall Box Filter Recommendation:
Waterscapes International BF1250 Pond Filter & Waterfall Spillway, 17-Inch
- $110.83
- Rugged high-density polyethylene shell with a lifetime warranty
- Comes with 17″ spillway, 1½” bulkhead, FIPT bulkhead fitting, media bag, filter pad, removable bottom grate, and liner attachment flange
- Ideal for small ponds and/or water gardens with a 2,000 – 3,000 GPH pump flow
6. Filter Media / Bio Balls / Bio Mats
Filter media can refer to polyester matting, ceramic rock, plastic ribbon media, plastic beads, and several types of hollow plastic media. Basically, any material that handles filtration. Media with larger surface areas are preferred, and styles can vary from filter mats, bio balls, brushes, and more.
Use a mix of different filter media to get the best results!
You can add filter media/bio balls/bio mats for better pond filtration. In fact, the larger the surface area, the more space for beneficial bacteria to grow and act.
Use a mix of different filter media to get the best results. Filter pads come in different densities and are chosen based on where they will be within the filter. Skimmer boxes work best with low and medium density pads, while your waterfall box should have high and super-high density pads for even more surface area. You can even buy pads and trim them down to size to suit your filter.
These types of media go well with any-size pond., and work as a great add-on for koi ponds. They are a highly effective, durable and natural means of improving biological filtration for reduced algae buildup. Bio balls are stored in a mechanical filter bag that can be cleaned and sprayed down to remove buildup. However, the filter pad or media needs to be removed and cleaned often.
Best for Any size pond. Filter media are a great add-on for koi ponds. They are highly effective, durable and a natural way to improve your biological filtration for reduced algae build up.
Pros and cons: Filter pads or media need to be removed and cleaned often. Items like bio-balls are stored in a mechanical filter bag that can be cleaned and sprayed down to remove the buildup.
Classification: Biological as they function to encourage beneficial bacteria to grow.
Nualgi’s Filter Media / Bio Balls Pond Filter Recommendation:
Bio Balls Filter Media – 1.5 Inch Large Bio Ball for Pond Filter
- $39.99
- Meticulously crafted from high-density plastic so they keep their shape
- Will never degrade
- Functions equally well year after year
- Buy 100, 300, or 2,000 large 1-1/2-inch bio balls with mesh bags
- Rinse and use
7. Gravity Fed Biofilters
These filters are used by all professional breeders and dealers in Japan. Biofilters promote the highly efficient growth of beneficial bacteria for healthy water and happy fish.
They enhance the growth of different ecological communities of bacteria and planktonic organisms that colonize different sections of the filter. The cross-flow pattern of most biofilters trap more dirt at high flow rates without plugging.
Best for: For medium and large ponds of up to 10,000 gallons.
With biofilters, you can experience superior water quality and reduced need for regular maintenance. Most allow for easy visual inspection, so the waste level and condition of the filter can be easily assessed. You can avoid blindly backwashing your filter every week. With a sloped bottom and extra sink, they generally have an outlet for the easy drainage of waste.
Biofilters come in both compact and large designs for big pond filtration. Most use a gravity flow design to eliminate moving parts from the filter and thus remove common failure points.
Pros and cons: Easy cleaning by backwashing the filter and pulling up on the handles inside the lid of the filter, but you need to be careful in what tubing and pump size you use with the filter for enough GPH.
We recommend you use a natural biological filter instead of throwing away helpful nutrients for bacteria since the aerobic bacteria eat the waste and cleanse the water. Biofilters come in both compact designs for small ponds and large designs for big pond filtration. Most use a gravity flow design, which eliminates moving parts from the filter and allows for more efficient water flow.
Classification: Biological as they function to encourage beneficial bacteria to grow.
With gravity fed bio filters you can experience superior water quality with less regular maintenance.
Nualgi’s Bio Filter Recommendation:
OASE BioSmart 10000 Pond Filter
- $324.00
- High-surface area filter foam provides exceptional biological filtration capability
- Up to 10,000 gallons (with no fish)
- Promotes the settlement of a variety of beneficial bacteria responsible for the different phases of the nitrogen cycle, which increases the conversion of harmful ammonia in your pond
- Includes a built-in cleaning indicator
- Water temperature display
8. Cyclone / Vortex Settling Tanks
This filter type removes the largest and heaviest waste from the water by using a vortex to pull particles through a cone-shaped bottom filter. They come with multiple chambers filled with media that catch floating waste.
As the water travels through the compartments, the dirt settles to the bottom and is automatically led to a drain which can be opened and flushed. The pond water leaves the filter after the last chamber and is sent back to the pond.
Vortex tanks come with multiple chambers filled with media that catch floating waste.
Chamber/cyclone/vortex filters require little maintenance since the chambers provide both mechanical and biological filtration for the pond water. About every two months or so, you will need to dislodge debris on the filter pads and flip the pads over.
Vortex systems are dependent on flow rate, and it is advisable not to send water through at a faster rate than the manufacturer’s recommendations. We have found that choosing a slower flow rate is a better choice.
Best for: Medium to extra-large ponds of 5,000 to 25,000 gallons, and that have organic matter settling at the bottom like koi fish waste, uneaten food, and leaves.
Pros and cons: These filters require little maintenance since the chambers provide both mechanical and biological filtration for the pond water. If you want a bottom drain, it can be very complicated to clean since you have to go underwater or drain the pond.
Classification: Combination of mechanical and biological as they function to provide both types of filtration.
Nualgi’s Vortex Pond Filter Recommendation:
GC Tek AquaBead 9.0 Bead Filter AB9.0
- $3,324.95
- Comes with a unique circulation pattern that spins solids to the center of the filter
- Features AquaBead sludge drain valve to easily collect and purge solids
- Max pond size: 25,000 gallons
- Flow rate: 180 gallons per minute
- Fish load: 450 lbs.
9. Rotary Drum Filters (RDF)
Rotary drum filters (RDFs) were once only available in commercial and industrial water filtration applications. They weren’t practical for koi pond hobbyists due to their size and prohibitive cost. However, new companies have now introduced RDF filtration options that are affordable and scaled down for residential koi pond installations.
Best for: Large to extra-large ponds of 5,000+ gallons
RDFs are an all-in-one koi pond filtration solutions. They can be used as a pre-filter or as a full combination biological and mechanical filter. Full combos include the air pump biological material area, and a turnkey to connect pipes for plug and play. Designed with only a few moving parts, they are designed to have low operating and maintenance costs.
Pros and cons: This all-in-one filtration system has automatic cleaning procedures and is low maintenance. But you need to keep a distributor or maintenance man available since fixes can be major issues. Ensure you manually wash the screen to keep up the flow rate.
Rotary drum filters are the most useful when there is excessive wastewater. They are versatile liquid-solid separation devices, and can be used for continuous filtration or where the continuous separation of a solid from a liquid stream is required. There are new models with smaller capacities suitable for home garden ponds, rather than for traditional use in larger industrial fish farms.
Classification: Combination since RDFs can be used as a pre-filter or as a full combination of the biological and mechanical filters.
Rotary drum filters are the most useful when there is excessive wastewater.
The system is industrially-made, with an expensive price tag to match. You also need to keep a distributor or maintenance man available, since minor problems can easily become major issues if left unattended. Ensure that you manually wash the screen to maintain the flow rate.
Nualgi’s Rotary Drum Filter (RDF) Recommendation:
- From $4,410.00
- Designed for water companies, fish farms and koi pond hobbyists that have high requirements for water quality
- Superb quality and sublime disposal of solids and dissolved particles
- Any solids down to 70 microns are caught in the filter screen
- Pond water filtered through the Profidrum RDF is pumped through additional filtration for further cleaning and returned to the pond
10. Bog Filter – Passive & Active
A bog filter is a perfect complement to a biological filter. What bog filters do is help to continue the nitrogen cycle that starts with biofilters. Biofilters house beneficial bacteria that convert the ammonia from fish waste into nitrates. Bog filters, which entail the use of bog plants, get the nitrates out of the water. Nitrates are a source of nitrogen so they function as plant food.
Without plants to feed off the nitrates, algae would have total access to the plant food. This would lead to the rapid growth of algae, leading to green pond water and string algae – something that you would want to avoid if you want a clean pond with happy and healthy fish. With a well-placed bog filter, you can ensure the bog plants will eat up the nitrates and starve the algae.
There are two basic types of bog filters, passive and active types:
Passive bog filtration
For a passive bog filter, all you need to do is to place your selected bog plants (e.g. common arrowhead, bulrush, horsetail grass, marsh marigold, etc.) in bare gravel with very little soil within the pond or in a section adjacent to it. Some people position the plants near the pond’s edge, holding them down with lava rocks. Either way, the plants are then forced to get nourishment from the pond water.
Active bog filtration
Active bog filters, on the other hand, entail the use of a pumping system, so water passes through the bog plant beds. There are downflow and upflow bog filters. Downflow types pull water down through the bog plant bed, so they tend to trap sediment and get clogged. This is why upflow bog filters are more popular.
In this setup, water from the pond is pushed upward through the plant roots and out of the bog plant bed. Some people have the water going through the upflow bog filter flow down some more biofilters before returning to the pond. Whichever setup you choose, the water goes back into the pond clean, with virtually no nutrients left for algae to feed on.
Best for: Any pond sizes from 500 to 25,000 gallons.
Pros and Cons: Requires very minimal maintenence and kept with minimal soil in the bog to allow plants to absord excess nutirents. However, the dead leaves and pond debris must be removed routinely.
Classification: Bog filters are mechanical pre-filters which are u sually made from foam pads which need routine cleaning.
A Gravel Bog Filter can be constructed in many different ways. You can find examples of common configurations on the link we provided to Nelson Water Gardens document. At the end of the document, you will find a tour that explains the following typical configurations of filters: Partition, raised, border, island.
In the linked article, learn how to plant the bog filter, suggested plants, plants to avoid, layouts of bog filters, and common errors while creating a gravel bog for your pond’s filtration. Good luck!
