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Myths, Mysteries and Fallacies

Filter bacteria: Fragile things?


The fables handed down through the years about filter bacteria include:

Certain chemicals would devastate the filter and pond of beneficial bacteria.

Washing out filter media with anything but pond water would wash off the beneficial bacteria.

High flow rates through the filter will wash off the beneficial bacteria

Major water changes would eliminate most of the disease pathogens in a pond.


Well it is not true. There are now numerous scientific studies that have proved beyond doubt that the Biofilm formation of bacteria that adheres to a solid surface is virtually indestructible. It is the leading cause of many nosocomial infections in hospitals growing inside of catheters, and implanted devices. This protective environment can exceed the mass of the microbe cell by over 100X, which makes it a very protective environment from the outside world. The industry has found that Biofilms are so resistant to destruction that is some cases water treatment plants have had to sand-blast the microorganisms from surfaces.

The medications that are commonly used in our Koi Ponds to eradicate pathogens will not fully penetrate these Biofilms in the filter systems to kill all of the beneficial or bad bacteria. The free-floating bacteria are killed more easily with chemicals. These chemicals are usually stopped in the beginning when it becomes depleted to inefficient levels when coming into contact with the Biofilm. Although a certain amount of growing Biofilm layers may be penetrated, or sloughed off but the newly exposed layers begin to grow that previously laid dormant due to the starvation from nutrients. The Biofilm now starts to rebuild its lost layers. This means that the most common result is a small Biofilm and large free floating bacteria kill rate.

The microbes in the Biofilm are almost bulletproof in this sphere of slime and can stay active for days and even weeks when fully dried out. Now one can understand why ponds recover so well after chemical treatment, and why diseases are never fully eradicated. It is due to Biofilm existence and its incredible protective properties.

Last Updated on Friday, 08 October 2010 14:16