After keeping koi for well over thirty years and having a really good filter which  I had designed that kept my water crystal clear 365 days a year, but the advice in those early years was to make your filter as large as possible (the volume of the pond is 5,500 imp gallons) so mine was over six foot long by two foot wide and three foot deep and as stated it worked brilliantly the only problem being it needed regular cleaning to keep the water flow at its maximum and it must have been doing a good job because I still have several koi over twenty five years old , but I decided that I had to do something about having to clean the filter so often, So I designed the filter  that I have been using now for the last eight or nine years. it needs cleaning no more than  three or four times a year and I call it GEORGE'S  MAGIC BOX it never slows the water flow and it is literally maintenance free, and  now the size has been reduced  down to only 42"x18"x30" deep.

GEORGE'S MAGIC BOX

• As you can see the filter looks very basic but believe me you do not need all the equipment that certain people will tell you that you need ,the secret to this filter is the water inlet it is a ventura  which increases the oxygen content enabling a larger culture of bacteria to thrive on the Japanese matting and the pea gravel.

•  

  The water from my pond goes via a 4"pipe to my sump or settling chamber from there it goes through Japanese filter matting which covers the inlets of my pumps (mainly to keep any blanket weed from entering the pumps and also to stop any frogs from entering the pumps) it is then pumped up aprox. 4 to 5 ft to my filter, first going into an empty chamber then UP through the Japanese filter matting cartridge over the top of the chamber then DOWN through the pea gravel into the next chamber then UP and through the outlet to my waterfall into my small koi pond down a small stream into the large koi pond and back round again.

   

http://koi-z-are-us.20m.com