A UV on Every Pond

Why All Ponds Should Have an Ultraviolet Water Sterilizer (aka Clarifier or UV Light)

The old school way of thinking was that the only thing a koi / goldfish pond or water garden needed was lots of plants to get rid of green water algae (algae bloom).  That’s only partially true, especially if you want your pond to be partially clear or clear only part of the time. 

Most times the old-fashioned plants-will-get-rid-of-green-water theory doesn’t work at all!

What naturally happens in any body of water, regardless of whether the water is in a fountain or large koi pond, is that sunlight combines with nutrients in the water to produce millions of tiny algae cells.  As the cells multiply the water literally turns green from the sheer number of tiny algae cells present.  This effect is increased with more sunlight and more nutrients.  A shady pond will produce less green water algae than one exposed to full sun.  Fish poop and dead plant material fertilize the algae adding to the problem.

It doesn’t matter, however, how shady the pond or sparse of fish and plants.  All bodies of water WILL turn green and most will STAY green and/or hazy.  It’s part of the natural processes.  We’ve even seen green water algae in indoor aquariums.  Some ponds and watergardens might clear up a little if they have enough shade and there is enough live plants in the pond to compete with the algae cells for fertilizer in the water.  This clearing, however, takes “forever” and never produces the crystal clear water that having a UV on the system will.   Then, once it has finally cleared it’s apt to go green again.

The only true way I know to clear a koi pond, goldfish pond or water garden of green water algae and – more importantly – keeping it from coming back is to install a UV Light. 

Getting rid of algae bloom is NOT the only thing a UV will do.  It will kill bacteria in the pond as well!  This lowers the amount of bad bacteria in the pond -- a big plus for koi or goldfish ponds where the health of the fish is the most important concern of the pond-keeper.   

We’ve read many articles that chastise the UV for killing nitrifying bacteria.  If they thought more deeply about it before they wrote their article they would see that a UV light does not diminish the effectiveness of nitrifying bacteria in well-established biological filters. 

A UV sterilizer can only kill what flows over its light.

Nitrifying bacteria clings to the walls of the pond and to the sides of the filtering materials used in the biological filters.  In general, they are not free-flowing so only a small portion of the pond’s good bacteria goes through the UV unit.  The only time the UV should be turned off for the sake of good bacteria is when the filter is trying to seed like in the case of a new pond.  A biological filter, whether it’s brand new or on a pond sterilized by a pH crash, needs all the help it can to “cycle”. That’s why we always say to turn off the UV until the biological filter is established.

On the same note, anaerobic (or bad) bacteria tend to flow with the water.  Think of New Orleans after Katrina.  The flood waters were filled with bad bacteria and a cause for concern because of the sickness and disease it carried.  The UV light is effective against this type of bacteria because it flows across the light.

For that reason, Ultraviolet Sterilizers work well (and are often placed) on indoor fresh and saltwater aquariums.  Many people now are finding the benefits of adding a UV sterilizer to their tap water source to kill any bacteria that might be remaining after chemical treatment.

UV Myths

A myth that was somehow created in the industry is that an ultraviolet water sterilizer will kill parasites.  Unfortunately, that’s not true in the practical sense although there’s a seed of truth to the claim.  If a parasite is held under the intense ultraviolet rays long enough it will kill it.  There are problems with this when considering the practical use of a UV to kill parasites.  Parasites cling to fish and only a small number of them will actually go through the UV.  Those few that actually make the trip through the UV go through so fast that the light only has time to give the parasite a slight tan.  In other words – don’t purchase a UV light to protect your fish from parasites – it just doesn’t work that way!  All you’ll end up doing is giving the parasites a tan.

Another thing the UV will NOT do is kill string or blanket algae.  Remember – the UV can only kill whatever goes through it. String algae sticks to the rocks, to the sides of the pond and to the plants.  It does not travel through the water.  We use AlgaeFix and Barley Extract or Bales to combat string algae.

How the UV Light Kills Green Water Algae and Bacteria

The lamp (or bulb) of the UV is inserted into a long quartz sleeve tube that is located inside a closed PVC vessel.  You won’t see the lamp burning – and you shouldn’t even look at it burning (!) – after all, it consists of concentrated ultraviolet rays that can damage your eyes.  The PVC housing has openings at each end (called ports) where the hose from the pump is attached so that water from the pond flows through from one end to the other.  The glass sleeve protects the lamp from water.  Water and electricity don’t mix and if there is a crack in the quartz sleeve the lamp and possibly the power supply as well will blow.

As pond water filled with green water algae spores and bacteria runs through the PVC housing and over the glass sleeve with the burning lamp inside, the UV rays from the lamp literally fries the free-flowing bacteria and algae cells.  It takes from several days up to a week or so once a UV is installed and running correctly on the pond for the water to totally clear up from the algae.  That can be hurried with initial water changes.

An ultraviolet water sterilizer (also called clarifier or UV light) has to be sized correctly and the water flow must be within proper flow parameters for the unit to work properly. 

Although the manufacturer might claim that an 18-watt UV light will work on a pond that is 2500 gallons, don’t believe it.  They lie!  Yeah, it might work if the pond is in a cave without sunlight and you add algaecides to kill the algae!  The size of UV you need on your pond will depend on your pond itself and the type of UV light you install.

The rate of which pond water containing live algae flows across the light means the difference between a well-selected ultraviolet water clarifier doing its job or not working to its full potential.  Several factors must be considered when sizing the UV light.  A longer tube, for example, will allow the water to get more exposure to the light – and that’s a good thing.  The simple fact that Emperor Aquatics’ ports are further apart than the ports of the Aqua Ultraviolet UV light means that the Emperor UV of the same strength as the Aqua UV will be the better choice.  The algae simply have more time under the light which produces a better algae kill rate.

The gallons-per-hour the pump puts out is probably the biggest concern we have with sizing a UV light.  You can, however, easily construct a UV bypass or order one through us that is custom designed so you can regulate how fast the water goes through the UV light.  Some units, by design, will tolerate higher flow rates than others.  Emperor’s High-Output models require very little, if any, slowing of the water so bypasses are not usually required.

On our Emperor Aquatic’s sales page, we listed our own suggested sizes of UV sterilizers for ponds of different sizes and sun-exposure, along with effective flow rates that allow the unit to work properly. 

I’m sure it’s pretty obvious that we prefer the Emperor brand of ultraviolet water clarifier – and that’s for many reasons.  Emperor Aquatics tends not to overstate their units’ effectiveness like so many other manufacturers.  We are very familiar with their products and have tested all the different models so we know what they can and cannot do.  The UV units they produce are of the highest quality and they design them to give optimal results – such as in the case of where the ports are located on the housing.  To top it all off their prices are competitive and they give terrific customer service (which is important to us).  

In a nutshell, a properly installed ultraviolet water clarifier will keep any and all ponds and water gardens clear of green water algae and help keep them healthier for koi and goldfish.  It’s important that it is sized properly and the pump and plumbing are working with it for optimal results.  That’s why many of our customers choose to purchase their equipment from us.  They know their choice will be the right one and that Pond Doc will be assisting them through the selection, installation and maintaining phases of their UV purchase.  You can call him at (770) 663-6325 or email him.

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