How to Choose an UVC for Your Fish Pond

Almost All Fish Ponds Go Green and Murky in Summer ... Except Those That Have an UVC Installed

In a well populated fish pond (I'm not talking about water gardens with lots of plants and few if any fish) you will need to install a system that will make sure that suspended algae that cause green water or even brown murky water are killed faster than they can form. And in warm sunny summer weather and when fish are fed with synthetic food it is certain that algae will form in your pond.

There is only one CERTAIN way to permanently solve your pond algae problem that causes green murky water especially in summer when weather is warmer and sunlight intensity greater. Buy an UVC ... ultra violet clarifier.

Algae are tiny plants and they thrive on sunlight, warm weather and high nutrient levels in water. The symptom of high concentrations are cloudy water ... often green pea soup-like or brown. You will not normally be able to see your fish during the day because the algae floats to the pond surface to catch as much sunlight as possible.

The fish in general do not mind the algae although if things get really our of control the excess algae can remove all oxygen from pond water and under this circumstance the fish will die from suffocation.

Green water ponds are rare in winter especially in the northern hemisphere because sunlight hours are less and water temperatures fall considerably. But when spring arrives and water warms up then the murky water re-appears too.

How to Specify the UVC

Most suppliers such as Tetra, Hozelock, Heissner, Oase, FishMate, Fluidart and Aqua Technologies essentially make similar units. They all claim to be the best but in practice there is little to choose and that's why if you buy a filter then go for one with an UVC included. One factor is very important in most systems (there is an exception and that is the FishMate range of filter and UVC combo units). The UVC must contain what is called a quartz tube since this doubles the efficiency of any UVC. It does however add to the expense. Always remember the UV light source must be replaced every 8000 hours or so (ie 1 year of full time use). The light source has been depleted of its UV radiation power after this period of time.

The table below is a good indication of the wattage (an UVC is specified in terms of wattage of power used to generate the ultra violet light) requied to treat the volume of water in the ponds shown. The greater the wattage then the greater the amount of algae infested water that can be treated. This is correlated to pond volume.

If you have extra fish and/or extra sunlight and/or extra high water temperatures then go for a bigger unit than this table suggests.

The UVC is normally installed in line just before the filter.

Table of sizes, pond volumes flow rates

1 US gallon (as used in this table) = 3.8 litres so 500 gallons is about 1900 litres

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