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Filters for Garden Ponds
Garden Pond Filters are a great way to keep the pond water clean, especially if you have a Koi pond. Let's face it, Koi are a type of Carp so they're going to be rooting around on the bottom of the pond and sending a lot of debris up into the water. A filtration system is highly recommended for those who happen to have the Koi pond. Pump filters also work primarily to keep the water pump from getting clogged and damaged by pond debris, so any pump that you put in the water should have some kind of filter pad.
Filters for the pond work like filters for the central air unit in your home, they any debris or dirt that happens to be in the water as it is pulled into the water pump hits the spongy filter and gets trapped. Most pond filters remove a lot of the larger kinds of debris such as decaying leaves, so it's not intended to take bacteria out of the water or remove excess algae that can be harmful to the pond life. Though there is a type of filtration system out there designed for that purpose, just make sure to read the information accompanying any filters thoroughly.
Besides the filter pad that protects the intake of water pump there are a few other types of filters specifically for cleaning the pond water. They are typically placed with a water pump so that the maximum amount of water can reach the filter to be cleaned.
The Other Types of Filter Systems
An Ultraviolet (UV) filter system is the kind that destroys algae. It combines the simple catching power of the filter with UV sterilizers. Every little algae, bacteria and protozoa that goes through the filter gets treated to a little UV sterilization. If you don't like dealing with that algae bloom every year this is a nifty system to have.
There are also biological filter systems that can be used to keep the water clean and clear. A biological filter can be lava rock containing beneficial bacteria placed somewhere along the pond pump system. The water will trickle through the porous rock and the impurities will get eaten by the good bacteria, while the water gets a free pass.
Mechanical filters do a pretty good job. They make use of materials like silica sand to purify the water. And they also work to remove larger debris from the pond such as pine needles and other decayed leaf matter.
A chemical filter would use something such as activated charcoal to purify the water. Many of our own water filtration plants use activated charcoal in part of the purification process of our drinking water.
All filtration systems need regular weekly cleanings to remove the debris that they snatch from the water and also clean the pumps intake on a weekly basis. You can usually clean the filters by running some clean water over them or by immersing them in clean water.