How to chose the right Koi filter
There are many different types of pond filter on the market and it can often be difficult to know which one to choose. When deciding on a filter we must take a few things into consideration first.
Koi eat a lot and produce a large amount of waste and create a large amount of ammonia through their urine and gills as they breathe. Because koi can grow quite large and produce large amounts of waste we need to provide them with large amounts of water. Koi are also very inbred and much weaker than a wild carp and for this reason alone we need to make sure that water conditions are good.
When looking at koi pond filtration there are two main types of filter. The biological filter and mechanical filter. Biological filtration happens inside the pond as well as inside mechanical filters and so we need to make sure that we get the mechanical filtration system right in order to help the biological filtration side of things.
Mechanical filtration is simply the process of removing solid particles from the water such as fish faeces, decaying leaves, algae etc. All a mechanical filter does is bring pond water into the filter unit where it is pushed through various filter media. As the water is pushed through the filter media the particles in the water are trapped in the media itself. They act as a sieve so that when the water is returned to the pond it is particle free. We then have to physically remove the build up of waste inside the filter to stop it from getting clogged up.
To achieve appropriate mechanical filtration you will need a good pump with the appropriate flow rate and wattage to give it sufficient power, and a mechanical filter. If the water flow produced by the pump is too fast then the particles in the water will not have a chance to sink and flow through the filter media. The mechanical filter itself will also need to be large enough to allow the particles time to sink.
Not everybody has space for a large filter but if you do have space then one of the best filters you can buy is the rotary drum filter. These are excellent filters but cost a lot to purchase.
Other methods of filtration are pre sieve filters, filter brushes, foams etc and all work on the principle of acting like a sieve by collecting the particles in the water as it flows through, and preventing them from flowing back into the pond. Unlike the rotary drum filter they will not get rid of the very fine particles and they all need to be maintained.
Biological filtration is needed in ponds and is fairly easy to set up. Some koi keepers use plants as their biological filters that will help to break down ammonia and nitrites into the less harmful nitrate. Inside filter media like foam pads beneficial bacteria will live and become part of the biological filtration process. If the mechanical filtration process is not working in your pond then the biological filtration will suffer as well because everything will become clogged up and prevent oxygen from reaching the beneficial bacteria. So in short if you sort out the mechanical filtration side of things then the biological filtration will take care of itself.
In an ideal world and with a big enough mechanical filter the water should sit inside the filter for 10 or more minutes before being returned to the pond. The filter system should turn over the entire water volume of the pond every 4 hours minimum.