A Guide to Modern Koi Pond Construction

Venturi.

Most koi-keepers use a venturi, and this is one of the most effective ways of getting oxygen into the water. It is general practice to buy one from a dealer and this is definitely the best way, and strongly recommended.
You can make your own, but they can now be purchased at a reasonable price.

The sketch on the right shows a standard type as purchased ready made, and this explains the general principle of how they operate.

The sketch above shows right angle bends, but those you buy now are designed to fit straight on to a piece of pipe through the pond wall. This can be seen in the left side of this photo where the pipes have been installed ready to receive the venturi.

The pipe through the wall is horizontal and not at an angle.

The photo above leftis is a common type of venturi you can purchase from most koi dealers. It can be fitted in the pond as shown in the two photos below, but many koi-keepers now put it in-line outside of the pond as shown in the photo on the right. The pipe returning the water to the pond is then flush with the wall and cannot let the fish damage themselves against the venturi.

TIP. If you have an existing pond with the venturi in the pond then in many cases you can remove it and fit it outside the pond as shown.

This photo shows a venturi in use, and you can see that it is working to good effect.
The top of the nozzle end is usually 9 - 12" below the pond water level.

This small close-up photo on the left shows the venturi in the larger photo.
In fig 21 the venturi is shown fitted directly on the end of the inlet pipe but it better to connect it with elbows and threaded joints as shown here so that the direction of flow can be adjusted.

Fig 22 above shows the general layout for the positioning of a venturi and a skimmer in a rectangular shaped pond.
It is only one of a combination of positions, but the general idea is that they are set well away from one another, and the venturi will create a current which will push any surface debris over in the direction of the skimmer, and it will then be drawn into the mouth of the skimmer when it is switched on.
Because it is difficult to design it correctly for the current to flow precisely in the right direction then adjustable pipework for the venturi is useful.
In the case of a well rounded pond as shown in the photos above then the venturi can be positioned so that the current goes around three walls before entering the skimmer.

This page updated October 2004