For years now there has been an endless variety of materials and designs used to filter water in Koi ponds. Materials have varied from hair curlers to magnets. Designs have varied from a simple wooden barrel filled with gravel costing as little as $12.00 to an elaborate system of vortex chambers, settling tanks, tank after tank of mat material, pressurized chambers, computerized costing upwards of $100,000 and covering close to a quarter of an acre. (See October 2002 issue of Koi magazine)
All these systems have one goal in mind. To filter the water in the pond so the fish can survive. Without a filter on a pond two things will happen. One, the water will not stay clear. Two, the fish give off waste in the form of ammonia. If this waste is not converted from ammonia to nitrites and then to nitrates within a short period of time by a biological filter the fish will literally die in their own waste.
The quest for the perfect filter has been foremost on the minds of Koi hobbyists since the hobby first began. Anyone who has been around this hobby for anytime is well aware that the only thing Koi hobbyists enjoy talking about more than Koi fish is Koi pond filters. When visiting a pond it is almost routine for the owner to show you his filter system. Having a really good filter system is right up there with having a beautiful show quality fish when it comes to "showing off".
The most common filter today is probably the simple ‘up flow gravel filter". This is simply a box filled with gravel or lava rock. Water enters the bottom of the box and filters up through the gravel and then returns to the pond. They work reasonably well depending on their size and are relatively inexpensive to build. Cleaning them can be a project though.
Bead filters were introduced to the market a number of years ago. "Bubble Bead" was one of the first on the market. The concept of using a floating material that could pack together in a very dense manner to serve as a filter media and yet be broken apart when needed to release the waste it collected was a stroke of genius. Today bead filter technology has advanced to the point to where many feel that it is the best filter system on the market. When we say it is the best it is with two exceptions. If money and room are not a factor I would be the first to admit that the large $100.000, quarter acre pond filter described earlier will out perform a bead filter any day. That being said, the bead filters today have several big advantages;
1) A small footprint. They only require about a four foot square area at most.
2) Remarkably easy to clean. With the new blower systems you can thoroughly remove all waste collected once or twice a week by simply turning a switch. The whole process can be done in about two minutes while you are in your suite.
3) The biological capacity (the ability to convert ammonia into nitrates) can be remarkable. This can allow you to stock more fish in your pond if you wish. (See Test Results of "Advantage Filter").
4) They are easy to install.
5) When you consider what your time is worth and how long it can take you to build a "gravel filter" it may turn out that the bead filters are not as expensive as they seem.
This is meant to be just a brief discussion of Koi pond filters.