An Overview of Koi Pond Filter Media

There are quite a few choices available today when it comes to koi pond filter media. Certain types of media are better for different uses; everything from brushes for great mechanical filtration to Japanese filter matting which works great at biological filtration. Many of these pond filtration media can be combined via multi chamber filters to create a custom tailored filtration system for your pond. Read on for an overview of some of the popular types of pond filtration media available.

Filter Brushes
A Filter Brush

Filter Brushes

Filter brushes are usually used as a mechanical filter, placed before the biological stages in a pond filtration system. They are usually made from a fish-safe polypropylene with a stainless steel wire core. When used as a koi pond filter media, filter brushes are very good at filtering out solids such as leaves, fish waste and string algae. This in turn helps to keep heavier solids out of the later filtration stages that are more easily blocked. Over time, brushes can become biological if care is taken when cleaning them. If rinsed with pond water every once in a while to keep the heavy solids off, beneficial bacteria will colonize on the polypropylene bristles, helping to clean the water on a biological level as well; although not enough to classify brushes as a dedicated biological filter.

Alfagrog - Porous Ceramic Material
Porous Ceramic Material (aka Alfagrog)

Porous Ceramic Material (aka. Alfagrog)

Like filter brushes above, porous ceramic filter media works very well when used as a mechanical filtration stage prior to the main biological stage. Also like filter brushes, porous ceramic is easy to clean, but can clog over a period of time if not backwashed now and then. The rough surface of this media with many holes and pores also provides a good surface for aerobic bacterial to colonize (a good thing).

caterbury spar
Porous Ceramic Material (aka Alfagrog)

Canterbury Spar

While canterbury spar is sometimes difficult to clean and can clog easier than some other media because it is quite dense, this media has a nice irregular surface which supports good bacteria growth. Also, because cantebury spar is quite dense it also has an excellent mechanical ability to filter out small particles, which is why it sometimes refered to as a water "polishing" media.

filter foam
Filter Foam


Open-cell foam is sometimes used as a filter media. It is installed in layers, usually on top of porous ceramic material mentioned above. Because it tends to clog quite quickly, it needs frequent cleaning. Unfortunately with each cleaning the foam is stripped of all beneficial bacteria making foam less than ideal for biological filtration.

Japanese filter Matting
Japanese Filter Matting

Japanese Filter Matting

Usually made out of polyester, this filter material is quite popular as a koi pond filter media. It is very lightweight and works well for biological filtration as long as it installed correctly. For a proper installation, the filter matting must be cut to exactly fit the width of the filter chamber and positioned such that the water can evenly flow through the supplied holes (if there are any). Japanese filter matting contains a large amount of surface area for bacteria to gro. However, it can sometimes take some time to establish a good culture of nitrifying bacteria. A bacteria additive can help increase the speed at which this occurs. A nice feature of this matting is that, unlike foam, solids are able to pass through relatively easily which prevents clogging. This helps cuts down on the cleaning required which helps the beneficial bacteria culture flourish.

We hope you enjoyed this overview of some of the popular koi pond filter media. Please have a look at the navigation bar on the left for more pond content.

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