What is a moving bed filter?
You may have heard of a filtration system called a bio bed or moving bed filter they are extensively used for waste water treatment all over the world. Well the koi world has picked up on this relatively simple technology for there pond filtration with fantastic results.
A moving bed filter or bio bed is essentially a container filled with water some sort of media and an air source to keep the media turning over similar to a general boil. This process allows a bio film to grow that will aid the removal of your pond nasties such as ammonia, click here for a more detailed look at this process via Wikipedia.
The added bonus of the bio bed filter is that is essentially self cleaning as the media is tumbling around removing dead bacteria allowing new to grow giving a low pressure filtration system up to virtually any size the more media in the moving bed the larger the bio film equaling better filtration, the ideal media to space balance is around half, so if you have an 80 litre moving bed filter the media sweetspot is approximately 40 litres. So the moving bed filter is the best with no need for any other filtration? Wrong! One of the only drawbacks to this system is that it is purely biological filtration you would need some sort of mechanical filtration first to remove any solid waste. The ideal koi filtration set up would be a mechanical filtration system like a pressure filter or static media bed like brushes, foams etc then a moving bed after this with its outlet back to the pond, it is a good idea to add extra bio filtration with a Bakki shower to give your water that sparkly clean finish. As your pond inhabitants grow you can add extra moving bed filters in your system to cover your needs.
What type of media is used in the moving bed filters? The main type is kaldnes media better known as K1 or K3 medias the K1 is pellet sized and the K3 larger sized disc around 2 cm, both work well in the system and are perfect for a moving bed filter system.