A pond venturi is a device added to the pond’s pipe-work, which injects air into the pond water as it passes through.

The venturi is a fantastic addition to a pond. There are no extra pumps or power cables required to run a venturi, it will simply work using the flow of water produced from the pond’s circulation pump.The freely injected air will increase the amount ofoxygen dissolved in the pond water, which is beneficial for fish, plants and for biological filtration. It will also increase the rate of gaseous exchanges in the pond, helping reduce the build up of dissolved toxic gasses.

How a Pond Venturi Works

The laws and concepts of fluid dynamics are quite complex, but the simplified principles related to the ‘venturi effect’ are:

• If a length of pipe becomes narrower, the velocity of a liquid passing through will increase.
• As the velocity of the liquid increases, its pressure will drop.
• If this drop in pressure becomes considerably lower than atmospheric pressure, air can be pulled in from a connected air tube.

The pond venturi is simply a constricted length of pipe with an air tube attached into the narrowest section. As the pond water enters this narrow section, the resulting difference in pressure sucks in air via the air tube. At the venturi’s outlet, the pipe widens and returns the now aerated pond water to its original velocity as it enters into the pond.A venturi can only be added onto pipe-work which is attached to a pump, and is therefore normally installed only onto ponds which have gravity fed filter systems.The aerated water emitted from a venturi can be quite turbulent, sometimes producing an undesired amount of noise or disturbing the pond’s surface. It is a good idea to add a flow control to the air tube, the amount of air taken in by the venturi can then be regulated for when you wish to view the fish, for example.