Koi Pond Filters

What is a koi filter?

Koi filters are large pond filters built specifically to filter large outdoor ponds, and with large fish like Koi.

How do koi filters work?

Typically koi filters do two jobs in ponds - trap fish waste, debris and dirt via mechanical filtration, and break down and convert liquid waste like ammonia via biological filtration. Water is fed into the filter box at the pond side where dirt is caught and beneficial bacteria dwelling inside the filter convert toxic waste into less harmful substances. The result should be clean, clear healthy water that’s good enough even for the most discerning Koi carp.

Do koi filters clear green water?

No, you will need a separate ultra-violet clarifier to deal with green water.

Can you use koi filters for other pond fish?

Yes, koi filters can be used with any freshwater fish from heavily stocked Goldfish to Golden orfe, Sterlet and Sturgeon.

What size filter do I need for my koi pond?

The most important factor when selecting pond filtration is the size of the koi pond. If the koi pond is 18,000 litres/3964 gallons for example you will need a koi filter which is purpose-built for koi ponds of at least 18,000 litres or more. The flow rate of the pump must then suit the filter and ideally, the pond will be purpose-built for Koi, with filtration being first and foremost in its design. Pond filters don’t have to be expensive but they do need to be capable of dealing with the waste products produced by your prized fish as they grow.

What else will I need for koi pond filters?

You’ll need a pond pump, a UV and some pond hose or pipework (depending on the model.) You may also need a pond air pump.

Do I need a gravity-fed or pump-fed koi filter?

That depends on how your pond is designed. 99% of serious Koi keepers utilise a gravity-fed filtration system fed by bottom drains. Bottom drains need to be installed in a concrete base using hard plastic pipes when the pond is being built. If you have a bottom drain and hard plumbing you need a gravity-fed filter. If your pond pump sits in the middle of the pond and uses a flexy hose you need a pump-fed koi pond filter.

What is a multi-chamber koi pond filter?

Nearly all koi filters used to be multi-chamber models, comprising a vortex prefilter, brushes, Japanese matting and alfagrog biological filter media all in different chambers. Multi-chamber filters are typically made from fibreglass and are still available. They have largely been replaced by compact koi filters or modular koi filters where users can mix and match chambers of their choice.

What is a drum filter?

A drum filter is a mechanical water filter that uses a rotating perforated drum to separate large debris from the pond water. Typically they are automated and rotate, moving dirty sections out of the flow and replacing them with a clean section. The drum is also cleaned automatically by a spray bar or washer jet which sprays clean water onto the dirty drum surface, flushing the debris to waste at the same time. A drum on its own is not a complete koi filter, and a separate biological media section is also required to convert liquid waste like ammonia.

What pump do I need for a koi filter?

For pump-fed filtration, you will need a filter pump, also known as a solids handling pump, which sits in the pond. Solids handling pumps have large intake holes to deal with all that Koi waste and their uneaten food pellets. Most koi filters and all UV clarifiers have a recommended flow rate so pair the pump output to the recommended flow rate of both koi filter and UV.

If the pond is gravity fed with a bottom drain and hard plumbing you’ll need an amphibious pump that sits next to the filter, outside the pond. Our specialist technical team can advise you on the right type and model of pump for gravity-fed koi filters.

What is the best filtration for a koi pond?

The best koi filters have separate mechanical and biological filtration and automated cleaning. That means they can clean themselves and flush water to waste without you having to get your hands wet. Koi filters with automated cleaning can clean themselves at night or even when you are away on holiday, and represent the state of the art in koi filtration. If the pond isn't designed and built yet, a gravity-fed koi filter with automated cleaning is the best you can get.