There are two types of biological filter. At home and higher. In a good water system for a small pond. Pump and filter system sits at the bottom of the pool. The system is relatively cheap, the downside is that when the filter needs cleaning (regularly, at least every two weeks) you are wet.
System above the ground is more expensive, but once installed they are easier to maintain and good for large ponds and pools with waterfalls. These pumps are generally stronger than the kind of underwater and can push more water. Filter is easier to change and clean.
When cleaning your filter system, both on land or in the pool, do not clean the entire filter system at once. Usually there is more than a filter pad or filter media chamber. Clean and half a time. You want to keep supply of beneficial bacteria in the filter system. Beneficial bacteria help our goods such as chlorine and sewage filters. It will also algae at bay.
Plants are also a nice pond for swimming. They provide shade and food sources for fish. There are floating plants like water lettuce, water hyacinth, Anacharis and Water Lillies. There is a marsh plant. It grows in a special pot and sat on the edge of the pool, such as iris, cannas and tail Cat. There are dozens of types of pool plants.This will add aesthetic beauty to the pond. It will also be a habitat for frogs and turtles.