Koi Pond Filters

All water contains impurities, such as ammonia and nitrite, that are harmful and can kill your Koi. Like any other living creature, Koi excrete urine and produce feces, and ammonia is excreted through the gill membranes. In the wild, natural ponds handle these impurities by diluting them in their large volumes of water, or washing them away in the running water that often feeds ponds. In your backyard, however, you'll need to have a filter to replace what Mother Nature does herself.

Mechanical filtration

Mechanical filters use a filling, called media, and settlement chambers to clean and purify the water. Settlement chambers allow gravity to drag the solid waste out of the water by slowing the water flow. These chambers usually come first in a filter, pre-treating the water before sending it through the media to remove the finer particles.

Biological filtration

This filtration method uses specific bacteria to break down toxic waste products and convert them to inert particles. This process uses a two-stage approach. The first stage breaks down ammonia to nitrite using nitrifying bacteria such as Nitrosomonas. The second stage is the conversion of nitrite to nitrate by Nitrobacter.

Both of these bacteria need oxygen to live. Since sediment building up in the filter depletes the available oxygen levels, it is important to keep sediment to a minimum by having a settlement chamber first and by cleaning the filter out occasionally.

A variety of filter media are available including gravel, matting, hair rollers, foam, and canterbury spar. They all provide s good surface for the bacteria to live on. On the down side, a biological filter will take weeks or even months to mature. You can buy cultures of nitrifying bacteria to l speed up the process.

Chemical filtration

Am ammonia and other organic waste products are removed by activated carbon using a process known as adsorption which causes the waste particles to become linked to the surface of the carbon. When the carbon surfaces can hold no more they must be replaced.

Zeolite can also be used to remove ammonia and nitrite from the water. Zeolite is "rechargeable" as it can be cleaned by soaking in salt water for 24 hours.

If a large biological filter is present then chemical filtration is not normally required, but is a good alternative to use use while the biological colony is maturing.

Sand filters

Some Koi owners use a sand filter as a final stage to 'polish' the water. Water passes through the filter, under high pressure, and comes out very clear. Desirable bacterial activity also takes place in the sand filter. However, sand filters are expensive to operate and clog too easily to be practical for fish or koi ponds.

Cleaning

Filters need to be cleaned occasionally to remove sediment. Most good filters have a bottom drain for each filter chamber so that sediment can be let out. Here's a timesaving tip: Put filter medium into net bags so it can then be easily removed from the filter later..

One last thing, NEVER put chlorinated tap water in a mature filter, it will kill all the bacteria and you'll be back to having to grow a new colony all over again.

Ultraviolet Sterilization

An ultraviolet (UV) system kills bacteria, parasites and algae living in your pond. In order for most harmful bacteria to reproduce, it must be able to float freely, in your pond, in order to find a suitable host. An epidemic of bad bacteria can spread throughout a pond and cause infection in your Koi.

UV systems are easy to install. The units are usually installed in the plumbing system somewhere after the pump and before the water enters the pond. Although your UV system should run along with your pump, 24 hours a day, it may not be necessary to run the lamps year round. UV systems are environmentally safe and not harmful to humans.