An Introduction to ULTRA VIOLET LIGHT Clarifiers (UVC's for short)

The one single piece of pond equipment that will improve the year round appearance of any water outdoor feature more than anything else is the UV light. Sometimes called an Ultra Violet sterilzer (even UV filter - it is not a filter of any kind). It does only one job: It kills suspended algae in any pond system. It works every time without fail so long as specified properly. All that has to be done to make sure it continues to work year in and year out is to change the UV lamp every 8,000 hours or so (about every year).

Here is basic information about UV light and what it does:

• Algae are plants and therefore need food and oxygen and sunlight to grow and survive. Like most of us the more food, the more oxygen and the more sunlight the better and bigger the algae grow. In the right conditions the algae grow at an explosive rate - 30 times per hour!!

• The usual problem encountered is that of green water sometimes brown which does not go clear and even after changing the water the algae re-appears very quickly and this happens even if you have a filter installed perhaps. Green/brown cloudy water is normally caused by these millions of algae remaining suspended in the water.

• Each algae is about 4 microns in diameter (1 micron is 1 millionth of a metre or very very very small). A filter cannot remove such small items.

• Algae growth is most common in ponds where conditions are most suited to their requirements - lots of fish being fed lots of food, warm water as it is in summer, and strong sunlight.

• When a pond is badly infected by green water then your fish can all suddenly die and this happens overnight normally. The reason is again simple and is because algae are plants ... they produce oxygen during the day but they produce carbon dioxide at night by taking oxygen out of the water. Algae in large mass can totally deplete the oxygen from a pond. The fish therefore suffocate. This is also very much more common in heat wave situations because at higher temperatures water can hold less oxygen anyway.

For a pond of around 250 gallons in full sun and highly stocked a 4 watt UV will do the job. This will also be big enough for a pond with very few fish and situated in the shade of 700 gallons. This assumes the UV comes equipped with a quartz tube to ensure the UV runs at peak efficiency. For a pond with average stocking an 8 watts UV will handle pond volumes up to around 1200 gallons depending upon sun/shade situation.