The addition of a filter to your pond is a wonderful asset, especially if you have incorporated koi into your pond. Koi are a type of carp, and therefore love to root around the bottom of the pond, sending debris into the water. A filtration system is great for cleaning the water and keeping in nice and clear so you can enjoy watching your fish! Pump filters will also work to keep your pump running smoothly, so only buy pumps that include pump filters!
Just like an air conditioning filter, a pond filter catches dirt and debris from the water as it pulls it in to circulate it through. The debris gets trapped on a spongy filtering. Pond filters are not meant to trap algae or bacteria, so please be aware that these substances can harm your plant and aquatic life if left unattended. There are filters that can deal with algae and bacteria, just make sure to read about the filter before you buy!
The filter pad that protects the pump is one type of filtration; others are also placed with a water pump because this is the location that reaches the maximum amount of water, cleaning it faster and more effectively.
Other Filter Systems:
An Ultraviolet (UV) filter is what you want if you are trying to prevent algae. This type of filter catches just like a regular filter does, but ti also has UV sterilizers. Any piece of algae bacteria that goes through the sterilizer will die. This is perfect if you do not want to combat algae each year!
Biological filter systems keep the water clean and clear. This included items like a lava rock that has good bacteria growing on it, placed in your pond. Water moved through the porous rock, being cleaned, impurities get eaten by the bacteria.
Mechanical filters work pretty well too. A good example is silica sand. They are able to remove larger debris, like pine needles and leaves.
Chemical filters usually need an activator, like charcoal to function. Charcoal is a popular water purifier; often use in many of the household water purification systems today!
If you incorporate a filtration system to your pond, make sure to check it regularly to see if it needs emptied and cleaned. It is also a good idea to check the pump intake when you do this to make sure there are no clogs. Run clean water through and over the filters to remove the debris and clean the filters!