UV (ultra violet) is the secret to crystal clear garden pond water.

Ultra violet light kills green pond algae. That is all it does but it does it extremely well and with total reliability. No fish pond should be without an uv clarifier.  No more pea soup fish ponds. The power of uv pond filters as some people call it or rather ultra violet light as it is more accurately known is a real advantage for the pond keeper. Blue ultra violet light is generated at a particular wavelength. It is a natural phenomenon and is one of the reasons we get sunburned on the beach. Do not worry about the detail but this graph below produced by Phillips shows plainly that at 40 degrees efficiency of UV is highest. At 20 degrees is it 50% efficient only.

Have you ever thought why we don't get sunburned from uv in the home behind glass windows? It is because ultra violet light is not transmitted through glass. It is fully transmitted through quartz however and this principle is used in designing aqua ultraviolet units or uv clarifiers for use in ponds.

Other names for ultra violet systems are uv filters for ponds or uv pond lights and so on. Even the term uv water purifier is used.

This is how an ultra violet light works in a garden fish pond.

Water is pumped through a quartz tube. In this way the pond water does not come into direct contact with the ultra violet source which is a miniature version of a fluorescent-type tube. This is important because uv light intensity is optimum at 40 degrees centigrade. If water impinged directly on the lamp the efficiency of the ultra violet light unit would be reduced dramatically because the temperature would then be lowered. Some units do not have quartz tubes fitted beware of these units. You must assume them to be 50% efficient only.

As water flows through the quartz tube ultra violet rays penetrate the water by direct incidence or via highly reflective metal surfaces. These ultra violet rays damage the cells walls of any pond algae circulating in the water (not any other type of green pond algae). In becoming damaged the green algae cells clump together and thus become much bigger than the 4 microns diameter as individual cells. The green algae is then able to be filtered out in the biolfilter.

The ultra violet light does not damage anything else in the pond environment. If the unit is designed to match the pond you can be absolutely sure of success and no more green water. Ultra violet or uv is all you need for success and no more green water.