POND WATER QUALITY
When we think of water quality, we usually think of two things: The waters ability to support aquatic life and clarity. Lack of clarity is usually not a problem for aquatic life, but it limits our ability to see our fish. The pond owner will be concerned with both of these aspects.
While it is true you can keep fish in an ornamental pond with no filtration, it severely limits the number of fish you can keep. In the wild fish have large amounts of water so that toxin from their waste do not build up to dangerous levels. Most hobbyists will want to keep more fish than their pond will naturally support. Fish excrete waste into the water in form of ammonia. Also adding to the problem are compounds from fish feces, plant matter and soil from both plants and washing or settling into the pond.
In order to provide good water quality some form of waste removal must be provided. The methods used in the average ornamental pond is mechanical and biological filtration. Mechanical filters physically remove solids by trapping the debris in some form of mat, brush or sponge. Most biological filters have some sort of mechanical filter but also have a large void area with biological material to allow large amounts of water to flow through carrying food to bacteria. These bacteria called nitrosomonas and nitrobacteria break down ammonia into nitrite and than into nitrate which is then food for the plants or for algae if plants are not available.
A biological filter must run continuously during the season and not be shut down for more than a few hours as the bacteria will begin to die. The filter should not be over cleaned, rinse the media only enough to allow good water flow thru the filter. The brown stain on the filter is living bacteria. We can increase the efficiency by adding concentrated solutions of bacteria and enzymes such as microb-lift or Aquascapes beneficial bacteria.