When raising Koi fish, it is vital that a suitable Koi filter is placed in the pond.
As Koi fish are extremely susceptible to conditions in their fluid environment, careful thought is needed when purchasing your choice of Koi pond filters.
Pond filtration is the method of eliminating waste matter and other harmful substances from the Koi pond.
This is a basic need if you want to keep your Koi alive for a long time.
  Without filtration, numerous events may occur:

1. The pond will turn to a green color.
   
2. Parasites and further damaging vermin will formulate and easily spread from one Koi fish to another.
   
3. The pond water will turn putrid and horrid, and will be deadly to the fish.
   

At the same time as preparing for aeration, preparing for the correct Koi pond filter is also important.
A poorly set-up filter system can damage the entire mission if it fails in a critical moment.
You can lose your most valuable specimens this way.
Some Koi experts suggest a Koi pond filter volume of not less that 33% of the total pond water volume.
For example, a 3,000 gallon pond should have a filter that is able to manage 1,000 gallons of pond water at any given time.
     There are two types of pumps available:

1.  Submersible pumps, recommended for small ponds and waterfalls because of their low profile and quietness.
   
2. Re-circulating pumps, suggested for larger ponds due to their effectiveness and long life span.
   

Any pond filtration system usually has two stages for mechanical filtering and another two for biological filtration.

• Mechanical filtration Consists of catching the debris and wastes in the water physically.
  The most commonly used materials are sand, beads, pads and brushes.
                      
• Biological filtration This system employs a natural biological system to convert the dangerous wastes into less invasive compounds.
  Koi expel ammonia, which in large quantities are deadly to themselves.
    Particular anaerobic germs convert ammonia into nitrites, which are also noxious to Koi.
    There are, however, good aerobic bacteria that convert nitrites into nitrates, which are harmless to Koi.
  These good bacteria are also known as nitrifying bacteria.
  

As well as these two Koi pond filter systems, there is also the bottom drain where foul water is sucked out by a pump for transportation to filter chambers.
  It should be placed in the deepest part of the pond bottom.
  A pond with no bottom drain will need to be cleaned regularly.
Owning an impressive Koi pond requires regular upkeep.
Picking the right choice of Koi filters is part of your Koi pond responsibility.
Having said that, caring for Koi fish definitely remains one of the most rewarding of activities.