New alternative mechanical Koi pond filter

How to build a mechanical filter using active bed media..

Active bed media can also be used as a static bed of media. Because it is very slightly buoyant, when there it no turbulence (i.e. air bubbles) it floats.

You can make a mechanical filter out of this very useful property of active bed media. Essentially a static bed of media functions by passing water into the filter in such as way as to cause it to flow through the static bed of media. By passing the water through this bed, any fine particles that are in suspension in the water are trapped within the bed, and hence a mechanically clean water stage can then be fed to the bio filters and hence crystal clear water is returned to your Koi pond.

The filter system makes use of an air backwash system that when activated turns the static bed of media into  its usual mode of operation - a hive of bubbling activity, causing all the trapped solids material to be thrown off in the process. The filter (chamber) is then simply drained along with all these unwanted solid particles.

Sounds a bit like a sand filter doesn't it?

Granted, it does. But there are several important distinctions between using active bed media and a sand filter that make all the difference in the world.

Firstly, active bed media is a much bigger media than a sand particle. The gaps between the media are much larger which means that the dreaded channeling that takes place in a densely packed sand bed simply doesn't happen.

This eliminates the build up an anaerobic zones that are the curse of sand filters. Even if the bed becomes really dirty, it will not clog with the ease of a sand filter.

The pressure drop across the bed is negligible owing to the larger media. This means you do not have to pressure feed the bed in order to get water to flow through it. This saves you on electricity.

The drawback to the bed however is that it does not take kindly to very high solid loading. It will of course work well even with filthy water but it will require regular back washing to keep the pond healthy (the same of course applies even more so to sand filters).

Very high flow rates through the bed are not recommended as this means that the really fine particles may not be trapped on the surface of the media simply because the water flow rates are too fast. That said however we have seen big static beds running at 220 000 litres an hour with no problems but under extremely controlled circumstances only... And definitely not practical for Koi ponds! Stick with our guidelines and you will be fine!