A koi pond requires a filter system that can handle both mechanical and biological filtration to maintain clean, healthy water. Mechanical filtration removes solid waste like uneaten food and fish debris, while biological filtration supports beneficial bacteria that break down harmful substances such as ammonia and nitrites produced by koi. Pressurized filters, gravity-fed systems, and multi-chamber setups are commonly used depending on the pond’s size and layout.
For larger ponds or those with a high fish load, a combination of a bottom drain, settlement chamber, and biological filter media works best to keep the water clear and safe. UV clarifiers are often added to help control algae, especially in sunny climates. The filter should be rated to handle the full volume of the pond, preferably with some extra capacity to account for the needs of growing fish.
