Garden pond filters

A pond filter traps particles and hosts the bacteria that break down fish waste. Choose it according to the water volume, the amount of sun, the number of fish and the time you want to spend on cleaning.

How to choose a pond filter?

Manufacturers often give several capacities for the same filter. The OASE BioSmart Set 36000 kit, for example, is rated for 36 m³ without fish, 18 m³ with fish and 9 m³ with koi: always go by the value that matches your pond's inhabitants.

• Volume and stocking: the more heavily stocked and sunnier the pond, the larger the filter must be. With koi, allow a margin.
• Location: a pressurised filter (BioPress, FiltoClear, TopClear, PondoPress) can be buried and placed higher than the water; a gravity-fed filter (BioSmart, MultiClear, Pond Clear) sits above the pond level and returns the water by gravity.
• Pond size: all-in-one submersible filters (Filtral UVC, Combi Clear) suit small, lightly stocked ponds; multi-chamber filters (Shark, Edouna) and screen filters (BioTec ScreenMatic²) are designed for large volumes and koi ponds.
• Built-in UV-C: many models include a UV-C clarifier that helps keep the water clear; otherwise, add a separate UV-C unit.
• Maintenance: backwash cleaning, a dirt indicator or a self-cleaning screen: this convenience matters when the filter runs all season.

Which type of filter for which pond:

Frequently asked questions

What size filter for my pond?

Calculate the volume (length × width × average depth), then choose a filter rated for that volume with fish, or with koi if you keep them. In full sun or with many fish, take the next model up.

Pressurised filter or gravity-fed filter?

A pressurised filter is easy to hide and can feed a waterfall placed higher up. A gravity-fed filter generally offers more filtration volume for heavily stocked ponds, but it must sit above the water level.

Is a filter enough to keep the water clear?

The filter traps particles and carries the bacteria that break down waste. For lastingly clear water you also need a suitable flow rate, UV-C, plants and a reasonable fish population: once this balance is in place, suspended green algae recede.

Should the filter be switched off in winter?

Many ponds stop filtration when the water turns cold. Then empty the filter, clean the foams and store the UV-C unit away from frost.

Which pump should I pair with my filter?

Choose a pump that delivers the recommended flow rate for your volume at the filter's real height, without exceeding the maximum flow the filter accepts. Complete kits offer a pump and filter that are already matched.

Read: the five questions to ask before choosing a filter, which pump and which filter for my pond (table) and how to hide a pond filter. See also the complete filtration kits, the pressurised filters and the drum filters.

Experts since 1998. Unsure about sizing? Write to support@foudebassin.com or call +32 10 86 03 54.