A Guide to Modern Koi Pond Construction

Prefabricated multi-chamber systems

There are many different types of these for sale and it is worth checking through koi magazines, the Internet, and local dealers to see what is available, and which is best for your needs and your pocket.

The most important thing to consider is the surface area of the filter in relation to the surface area of the pond. The filter cannot be too big and it has been found to work well when the surface area of the filter is one third the area of the pond. Meeting this criteria often means that they are quite expensive.

1. On the left (A) we can see the drains box. The drains for each of the filter chambers will be piped here and fitted with a valve. The overflow pipe will also be run to this box. A 4" pipe is connected to the main drains. In many cases this is supplied as a separate unit or can be made with concrete blocks.
2. In this case there are three filter bays. It will be seen that the bottom of the filter bays (B) are sloped away so that any solids slide down towards the bottom drain, and can easily be flushed away. This is a desirable feature, but many units are supplied with a flat base.
3. In the bottom of each bay there is a perforated PVC tray (C) which supports the filter media.
4. There has to be transfer ports (D) between each bay so that the water leaves the top of the filter bay, and enters the next one below the media. This can be as shown here, a flat weir, or 4" pipes.
5. In the last bay there is the suction for the pond pump. This should have some type of basket so that leaves, debris, or filter media is not drawn in.
6. An overflow is usually incorporated in one of the bays so that the pond water cannot go above a designed level.

We can now see installing a fibreglass unit.