Pond Filtration
Naturally existing ponds are kept healthy and in balance by natural processes, but a pond filtration system is beneficial for many constructed ponds. Pond filters work to remove suspended particles, dissolved pollutants, fish waste, and excess nutrients that promote unwanted algae growth.
The three primary types of filtration are mechanical, biological, and chemical. Mechanical filtration removes suspended particles and debris by physically catching particles. Chemical filtration uses substances such as carbon or zeolite to remove toxins from the water. Biological filtration encourages growth of beneficial bacteria to keep water in balance. All pond filters contain one or more type of pond filter media, and some can be interchanged based on specific needs of the pond.
External pond filters are located out of water, in close proximity to the pond. They can be partially buried but must be above the water level. Output from the pump is directed to the filter, trickles through its filtration layers and back into the pond. Being superior at biologic pond filtration, these filters are the best choice for increasing the fish capacity of a pond. They are generally used for larger ponds because they perform well but are large and can be an eyesore, particularly with small ponds. Various types of filter media can be used in external filters. Typically they contain a foam layer for mechanical filtration as well as porous substance for biologic filtering or other media for specific purposes.
Submerged filters are smaller and located within the pond itself. Like external filters, they often contain several types of filter media for mechanical, chemical, and biologic filtration. They can be attached at either the pump inlet or output, but are commonly connected at the inlet to protect the pump. This configuration also allows water output from the pump to drive waterfalls or fountains within the pond, something not possible with external filters.
It is often practical to use more than one filter in combination, particularly with larger ponds or ponds that support many fish. For example, a small submerged filter may be located at the pump inlet to protect the pump; the water may then be directed through an external filter to remove additional pollutants for clearer, cleaner water.
Filtration is an important component of any garden pond. Whether it is as simple as running a waterfall over rocks, or a more complex commercial system, pond water filtration keeps garden ponds clean, clear, and healthy.
