Aquatic Ponds

You will want to match your pond filtration system with the amount of water you have in your pond, the amount of pond fish you expect to have including size of your koi.

Many of the fish pond filters will have mechanical and biological filtration.

Mechanical will physically remove debris and waste from the pond by filtration materials, such as foam pads, that trap suspended particles. Other filters that do not have a foam pad will develop a slime coating on the filter media and then particles will adhere to it.   

A bio pond filter will have some kind of bio media for growing bacteria. This will aid in removing the harmful effects of organic waste and ammonia.

A UV Pond Filter will have the advantage of clumping suspended algae and trapping it in your filter keeping your water clear from green water.