Basic UV (Ultra Violet Light) Facts To Control Suspended Pond Algae

All ponds should have an ultra violet light (UV, or UVC or UV filter and also called UV sterilizer ... these all refer to the same thing).

This piece of pond equipment is probably the best pond invention ever since it guarantees clear water when sized correctly and maintained annually

Pond volume, stock density and sunlight intensity is required to specify correctly the size of the Ultra violet (UV) light you need to prevent algae making your pond go green

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 the sun/shade situation.

The rule you always need to bear in mind is as follows and it remains as a guide only:

• Lots of regular sun (like South Africa) .... consider more UV power

• Lots of fish (most ponds) .... consider more UV power

• High water temperature consistently (above 20 degrees C or 70 degrees F) for longish periods .... consider more UV power

If you have all three in the same situation almost certainly you will need more UV power and my suggestion is to double that "theoretically" required.

If you ever find that suddenly it appears that your UV is not working anymore consider the following potential causes

• Lamp needs replacing (they only last maximum of 1 year in continuous use) and sometimes much less but before you rush out and buy a new one ...

• Check the quartz tube is totally clean and transparent ... this tube often gets coated with fine layer of solids preventing full UV power being exposed to circulating water.

• As fish grow and multiply any UV that was on the borderline of its capacity can no longer cope. In this circumstance get rid of some fish or if you find you have specified an UV that is too small it is possible to add an extra one of the same size. For example 2 by 4 watts units is the same as an 8 watts unit. Pipe them up in series rather than in parallel.

To conserve lamp life you can switch off the UV at night if you really want to but it is not recommended. This will allow your UV light source to last longer. In winter, in cooler climates, it is ok to shut down the UV light.

It is normally a good idea to put the pump on the same circuit as the UV light to ensure the UV runs continuously but shuts off if the pump shuts down ... when an UV runs without circulating water solids tend to deposit (water remaining in unit evaporates leaving solids behind) on the quartz tube surface. Be very careful of this if you swith an UV lamp off every night.