How to Use a Koi Filter

As discussed previously in the Koi Care article, the quality of the water in your pond is vital to the health of your Koi. Quality water is a result of proper pond size and filtration. 

Koi are very sensitive to the chemistry of their water, much more so than other fish. Special consideration is needed when selecting the filter that will keep your Koi healthy and happy for their long lives.

A Koi pond filter is your first line of defense to balance the water chemistry. The filter’s job is to remove the waste product produced by your Koi. In a natural pond, waste is filtered through a combination of the volume of water, natural current, and plant life.  In a man-made Koi pond, a filter is necessary to replicate this effect. 

Most filters available commercially have two purposes – to filter water mechanically and biologically.

Mechanical Filter...

A mechanical filter pulls solid waste out of the pond water, trapping it in the filter.  Cleaning the mechanical filter component regularly helps keep it working smoothly.  Your mechanical filter keeps the pond’s water clean of chunks of solid waste. 

Biological Filter...

The other component to a quality Koi pond filter is the biological filter. It relies on beneficial bacteria to break down the toxic chemicals in fish waste. Like their cousin, the goldfish, a Koi’s waste is high in ammonia. Too much ammonia in the water will burn your Koi, much like household chemicals can be irritating to our skin. A biological filter breaks the ammonia down into nitrates, which are much less harmful to your Koi friends. The biological filter also helps maintain the proper pH level for your Koi – between 6.8 and 7.8.

Pumping Device...

Finally, your pond filter needs a strong pump to force the water up into the filter and then back out into the pond. Another great addition to your Koi pond filtration system is a small water pumping device like a fountain or waterfall. Not only are these beautiful for you and your guests to watch, they also mix oxygen from the air into the water. This process, known as aeration, is very healthy for the fish.