What Pond Filters Do
Pond filters can serve a variety of functions, including:
- protecting the pump from debris
- breaking down dangerous fish waste
- trapping some suspended particles from the water
- removing some dissolved waste from the water
- reducing algae growth by removal of nutrients
What Pond Filters Don’t Do
Unfortunately, what typical pond filters aren’t designed to do is to single-handedly keep water “crystal clear” - at least not to the extent that aquarium filters do. In fact, a filter adequate to keep even a small, 200 gallon pond as clean as an aquarium would have to push about 1500 gallons per hour and use a filter cartridge approximately four feet by six feet!
But Danner Manufacturing proposes a great variety of pond filters which can keep the water crystal cleer.
Types of Pond Filters
Intake Filters are usually small (perhaps 3x3x6 inches or so) blocks of open-celled foam that often come in the box with the pump. These are far too small to be effective at waste removal or reduction, and serve only to prevent pieces of debris from being sucked into the pump’s intake and stopping or damaging the pump itself. Advantages: inexpensive; easily removed and rinsed clean; output of pump can still be used to run fountain or waterfall. Disadvantages: small surface area means they plug with debris quickly; often need to be rinsed daily or even more frequently; do not improve water quality significantly. Things to Look For: very coarse foam for good flow; firm attachment to pump; multiple filtering surfaces so a single leaf cannot block flow.
Submersed Filters are generally larger and more versatile than intake filters. A reasonable unit for a small pond might have a surface area of a square foot or more, and may use a variety of filter media including coarse and fine pads for mechanical filtration, carbon or zeolite for chemical filtration, and perhaps some sort of plastic or porous stone media for biological filtration. Many units can be installed on either intake or output side of the pump, but are most commonly connected to the intake where it protects the pump as well as cleans the water. Advantages: improve water quality as well as protecting pump; may go days to weeks between cleaning; optional filter media may be added for special purposes; pump output may still be directed to water features. Disadvantages: pondkeeper may need to wade into pond to retrieve filter for cleaning; much waste from filter may spill back into pond during cleaning; take up valuable space inside pond. Things to Look For: easy disconnection from pump; large surface area; room for several different media; filter media compartment recessed enough that waste isn’t spilled when removing from pond.
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