Filtration is one of the most important components to maintaining a healthy pond. There are many different types of filters on the market and it can be a bit confusing deciding which one is right for you.
A few of the most common types of filters include Internal, External, Skimmer, and Biofall Filters
To make the most informed decision it is important to understand the types of filtration.
Mechanical filtration is using filter pads to physically remove floating algae from the water. The bigger the filter the less often it will need to be cleaned, but even the largest filter pad will not be enough by itself. Biological filtration is also vital to maintaining clear water and a healthy eco-system.
Biological filtration consists of some sort of 'bio-media' which grows bacteria to properly break down fish waste and eat up nutrients that promote algae growth. There is beneficial bacteria on every surface in a pond. A biofilter adds to the amount of surface area for bacteria to grow.
Chemical filtration is the use of carbon in the filter to remove some chemicals that are dissolved in the water. These chemicals are responsible for discolored water, usually yellow or tea colored, and can be the source of unpleasent odors. There are two ways to have carbon in a filter, bags of loose carbon or pads that are fortified with it. The pads are the most commonly used and they should ideally be replaced every two months. After this amount of time the carbon is saturated and no longer effective. This type of filtration is of limited usefulness in ponds. While it is very effective at removing organic waste, it is expensive and you can accomplish the same thing with water changes.
Most pond filters utilize a combination of Mechanical and Biological Filtration.