The most important factor for raising high quality koi is water quality, and the best combination to control water quality is Bio Sponge and Filter Sand.
When considering previous practices, filter mat and brushes have been used for years in the koi keeping world, however they are only efficient at collecting waste, which can then turn into sludge. Therefore, it is not too much to suggest that the combination of filter mat and brushes is an effective way of producing sludge in a filter.
Sludge is detrimental, organic matter, and is the main cause for deterioration of water quality, as it causes a pond’s pH to drop. Also, sludge breeds germs and increases the risk of disease and illness in a koi pond.
In summary, filter mat and brushes can contain and collect waste, but cannot clean water.
It’s important to point out that there are two types of filtration.
First, there is physical filtration, which means physical waste is collected (typically via filter mat and brushes). Second, there is biological filtration, which is the process in which waste is resolved into inorganic matter. Proper filtration only occurs when both of these processes are working in tandem. There are many filtration systems where the biological element is not as efficient as it should be. While these filtration systems contain bacteria, one can easily differentiate between bacteria working optimally, and bacteria which is not working sufficiently. One example of this is the occurrence of white foam on the surface of a pond. This means the bacteria are not working as well as they need to be, which could lead to a variety of diseases or other problems in koi.
In regards to clean and good water for koi, there is a current compulsion to have drum filters on our ponds. Without question, the water looks clean, but from the koi’s point of view, “What choking water!”
While the water quality may look good, there may be, in fact, high levels of Ammonia and Nitrite in the water. Ammonia and Nitrite are poison for koi, so let’s change places for a moment – koi with human. How would these conditions affect humans if we were kept in a dirty pond with Ammonia and Nitrite?
Koi would want to run away from such a pond, and have decreased appetites.