Finding the Best Filtration System for Your Pond

by Tory Jon | Last Updated: October 06, 2024

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Comparison Chart

	Description	Awards	Price
	Pond Boss Filter Kit FM002P	Best Small Pond Filter System		Buy on Amazon
	OASE BioSmart 5000 Pond Filter	Best Koi Pond Filter		Buy on Amazon
	Goplus 4-in-1 Pond Filter System with Fountain	Best Pond Filter Fountain		Buy on Amazon
	OASE BioSmart 10000 Pond Filter	Best Large Pond Filter		Buy on Amazon
	Aquascape BioFalls 1000 Filter for Pond Waterfall	Best Pond Waterfall Filter		Buy on Amazon
	Polar Aurora 4000L Pressure Bio Filter	Best Pressurized Pond Filter		Buy on Amazon
	Jebao CF-10 Pressured Pond Bio Filter	Best External Pond Filter and Best Pond Filter With UV Light		Buy on Amazon

*Buying through links in this chart may earn us a commission at no additional cost to you.

Pond Filter Systems Compared

Pond Boss Filter Kit FM002P

• Best Small Pond Pump and Filter System

The Pond Boss pond filter kit with pump is an eco-friendly, energy-efficient pump and filter combo that is one of the best values you can get for the dollar!

This filter comes complete with an energy-efficient 320gph pump, two filter pads, ten bio balls that help promote beneficial bacteria growth, a water spray nozzle (for pond aeration) with extensions, and a diverter valve. It also features a long 16ft power cord and a 1-year product warranty.

Perfect for garden ponds up to 500 gallons of water.

OASE BioSmart 5000 Pond Filter System

• Best Koi Pond Filter

The OASE BioSmart 5000 pond filter is arguably one of the best bio filters for koi ponds (or any pond) on the market. It comes in 5,000 and 10,000 gallon (our top pick for large ponds below) models, which is basically the size of the pond that they are suited for, respectively. Keep in mind, if your pond is stocked with koi or other pond fish, then the max size goes down to 1250 gallons of water (2500 gallons for the 10000 model).

The BioSmart external pond filter box provides mechanical and biological filtration with distinct filter zones that promote the settlement of beneficial bacteria.

And probably my favorite feature is how easy this model is to clean! Gone are the days when you would have to take apart and manually clean all the different filters. There's a built-in cleaning indicator with the BioSmart pond filter cleaning system that lets you know when it needs to be cleaned. Then, you simply pull up on the filter handles, and it drains any debris through its built-in drain while keeping the beneficial bacteria intact!

It has a maximum flow rate of 2700 gallons per hour (GPH) and comes with a solid 3-year warranty.

Goplus 4-in-1 Pond Filter System with Fountain

• Best Pond Filter Fountain
• Best All in One Pond Pump and Filter

The Goplus 4-In-One Pond Filter System is a unique fountain, filter, pump, and water purification system - all in one!

It features four different levels of filtering - a 9 watt UV clarifier, a mechanical filter pad, and three biological filter baskets (two filter stones and a filter ball basket). Plus, three different fountain spray nozzles!

This filter system is rated at 660 gallons per hour (GPH).

On the downside, while it is a highly rated filtration system, and I’ve never had an issue with one, it only comes with a 1-year warranty.

OASE BioSmart 10000 Pond Filter System

• Best Large Pond Filter

The OASE BioSmart 10000 pond filter, as mentioned above, is perfect for larger ponds up to 10,000 gallons of water (without fish). With small fish, the max pond size is roughly 5000 gallons, and if you stock koi, then the max pond size is 2500 gallons of water.

Aside from the max pond size, the only main difference between the BioSmart 5000 and the 10000 are the max flow rate (the 10000 comes in at a max flow rate of 3600 GPH, 900 more GPH than the 5000).

Aquascape BioFalls 1000 Filter for Pond Waterfall

• Best Pond Waterfall Filter

The Aquascape BioFalls 1000 filter is an excellent option for those who want a waterfall feature in their pond.

This filter comes in 4 different sizes: 1000, 2500, and two 6000 max pond size options. Each size jump has a larger spillway lip (15 inches, 21.5 inches, and 28 inches, respectively).

The Aquascape filter system provides biological and mechanical filtration, a max flow rate of 3000 GPH, and comes with everything you need to be up and running quickly and easily.

And it also comes with an industry-leading limited lifetime warranty!

Polar Aurora 4000L Pressure Bio Filter

• Best Pressurized Pond Filter

The Polar Aurora 4000L is a pressurized biological filter that features a 13-watt clarifier.

This powerful pressure filter has a max flow rate of 4000 GPH and is perfect for ponds up to 2500 gallons with a normal fish load and 1500 gallons for ponds with a lot of fish.

This filter is super easy to clean with its backflush feature and even has an indicator to let you know when it needs to be cleaned.

You’ll be up and running in no time with this filter since it comes already assembled. Just hook it up and enjoy a clean and clear pond.

Jebao CF-10 Pressured Pond Bio Filter with 13W UVC Clarifier

• Best External Pond Filter
• Best Pond Filter With UV Light

The Jebao CF-10 Bio Pressure Filter is an excellent external filter that offers three layers of filtration - mechanical, biological, and ultraviolet!

Jebao put a lot of thought into their UV clarification system. This canister filter slows the water down as it passes through the UV light to kill more harmful algae spores, and they use a quartz glass tube to cover the light as regular glass can cut UV light penetration by 90%!

This canister filter provides filtration for ponds up to 1500 gallons (without fish). If you have a regularly stocked pond, it’s good for 1000 gallons, and if the pond is stocked with koi, 500 gallons.

Recommended for use with pond pumps between 850 and 1250 gallons per hour.

Wait, Do You Need a Filter for Your Pond?

Wild ponds aren’t equipped with filters, so why do most cultivated ponds have them?

First of all, a small pond that’s not intended to support animal life, nor does the pond owner care that the water gets a little murky, might not need a filter at all. Manually removing debris (or just using a pond net) and a careful selection of pond plants may be enough to keep the water clean and suppress the growth of undesirable algae (learn more about how to clear murky pond water).

However, many pond owners stock their ponds with fish and/or really enjoy a crystal-clear pond. Keep in mind that a wild pond's lifecycle includes stretches that most property owners would consider problematic. Beneficial bacteria levels can drop dramatically, and algae blooms can dominate natural ponds during the summer months, pond water can become murky, and so on.

This is where proper filtration comes in. Backyard pond filters help to keep a cultivated pond from enduring the extremes to which wild ponds are subject.

A pond water filter helps keep the water clear by removing organic debris and encouraging the growth of beneficial bacteria. Organic waste is produced by fish excrement, uneaten food, and pond plants losing leaves or roots. Other debris originates outside the pond and falls or is blown into it. This waste eventually makes its way to the pond filter, where it is trapped until the filter is cleaned.

Filters also break down contaminants at the chemical level. Ammonia and nitrites can quickly rise to hazardous levels when fish waste and other organic material are left to decompose in a pond. The bacteria that thrive in pond filters break ammonia down into nitrites and nitrites into nitrates, which are put to good use by beneficial pond plants and algae.

So, whether you make your own DIY pond filter or buy one from the store, in almost all cases, I recommend using a pond filtration system.

Types of Pond Filters

There are three main types of pond filters: submersible pond filters, external pond filters, and pond skimmer and waterfall filters.

Pond water can be filtered through one of the above types of filters by different means: mechanically, biologically, and/or by ultraviolet light.

Mechanical filtration is when water is drawn through filter media, often a foam or fibrous padding, and traps debris. This type of filter requires regular maintenance and cleaning.

Biological filters contain media that encourage beneficial bacteria to grow (by maximizing surface area) and are usually made of pebbles, plastic spheres, ceramic rings, beads, and so on. Where mechanical filters just trap debris, biological filters take that a step further and break down ammonia and nitrites that form the true dangers in ponds clouded by organic waste.

Ultraviolet (UV) filtration, also called UV clarification, controls pond algae and contaminants by killing harmful bacteria and algae, reducing the direct negative effects of those undesirables, and allowing beneficial forms to filter the water more effectively. It works by exposing pond water to ultraviolet light that penetrates the cell walls of harmful organisms. This takes time, and UV filtration systems must move water relatively slowly to achieve full results. Some systems circulate the water within the filter itself to encourage sufficient exposure, and many use high-powered lamps of up to 50 watts (though 13 watts seems to be most common).

Aside from new UV lamps every year, UV light systems themselves incur little maintenance. Just keep in mind that pond UV clarifiers typically work together with other filtration methods because they do nothing to physically remove the organisms they kill.

Now that we understand the types of filtration let’s look at the different types of pond filters you can buy.

Submersible Pond Filters

Owners of smaller ponds often choose to keep the filter entirely out of view by installing it underwater. They consist of a pond pump fitted with a mechanical or biological filter on its intake side.

Because they are best installed when ponds are dry, submersible filters are designed primarily for use with smaller, often preformed, or lined ponds. They can be purchased separately but are often sold together with pumps and other accessories such as fountain heads or diverters.

Modern submersible filters are easier to maintain than early models, but they still must be removed from the water, which may be inconvenient for some owners.

External Pond Filters

Because they sit above the water, external pond filters are more versatile than submerged filters and tend to be far more durable. Free from the space considerations of submersible filters, external pond filters tend to be much larger, giving them the capacity necessary to treat larger ponds. The same factors allow external filters to combine filtration methods and media in ways not possible for submerged filters.

Because they receive water directly from a pump, external filters benefit from a mechanical pre-filter fitted to the pump's intake side to trap large particles before they clog more finely-tuned filter media. Because of this, external filters themselves are much easier to clean than submersible pond filters and tend to require less maintenance overall. There are self-cleaning pond filters, as well, but expect to pay a premium price for this added convenience.

External pond filters move water through either gravity or pressure. A gravity-fed pond filter setup brings pumped water well above the water’s surface and allows it to flow along filtration media before returning to the pond. Because they rely so heavily on natural forces, gravity pond filter systems are highly efficient. However, they may need to rise several feet above the pond’s surface, making them an inelegant solution for some settings.

Pressure-fed or pressurized external pond filters rely on the pump’s force to move water through filter media. This approach can be implemented in an easily concealed enclosure, making it more versatile in some ways than gravity-fed filtration systems. But pressurized pond filters require a bit more math.

While pressurized pond filters can be placed anywhere near the pond, their distance from the pump is crucial. Pond owners who plan to install pressurized filters should be sure that pumps produce enough power to drive water through the filter and should be ready to add one pound of power to their calculations for every ten feet of distance from the pump to the filter.

Despite the necessary number-crunching, pressurized pond filters are the most common type, especially for larger ponds. Paired with a sufficiently powerful pump, a pressurized filter can be placed anywhere and can be easily concealed. Its outflow needn’t simply drop back into the pond, as with gravity filters: it can feed waterfalls or other water features, which themselves can be fitted with mechanical or biological filters.

Pond Skimmers and Waterfall Filters

Many owners of large ponds augment traditional filtration systems with other types of filters. Chief among these are pond skimmers and waterfall filters.

Pond skimmers sit just at the top edge of your pond’s water, where they draw in leaves, sticks, and other surface debris before they have a chance to decompose and settle on the pond’s floor or clog the main filter. Some pond skimmers house integrated or in-line pumps, making them great solutions for small ponds.

In small ponds with little or no animal life, pond skimmers may prevent the need for more elaborate filtration systems. In larger ponds, they protect other filtration equipment, extend the life of filter media, and reduce the need to disrupt colonies of beneficial bacteria.

Because waterfalls implicitly involve water being moved by gravity or external pressure, they are popular sites for supplemental filtration. Mechanical or biological filters are usually fitted to the top of the waterfall, where they are easily concealed. Filter enclosures often include a weir or lip that spreads filtered water across a wide area before it spills over the waterfall’s edge.

Pond Filter Size Guide

A pond’s primary filtration system should be rated for roughly 1.5 times its volume. A pond containing 300 gallons of water should have a filter rated at 450 gallons per hour; a pond of 1,000 gallons requires filtration rated 1,500 gallons per hour.

Calculating a pond’s volume is nearly as easy, especially if you use our free pond calculator! It will tell you your pond's volume, the size filter it needs for optimal filtration, and much more. But, if you like to do things the manual way, here you go...

How To Calculate Your Ponds Filtration System Needs

For rectangular ponds, multiply the base volume (length x width x depth) by 7.5 to find the volume in gallons.

For oval ponds with vertical sides, multiply the same base volume by 6.7.

For circular ponds, multiply the pond’s depth by the square of its diameter, and multiply the result by 5.9.

Irregularly shaped ponds present a bit of a challenge. Some ponds can be broken into a few easily measured components, which can then be added together. Others require a good deal of estimation, in which case pond owners should always err on the side of generosity.