Ultraviolet Sterilizers

Ultraviolet [UV] Sterilizers are useful in helping to control bacteria, algae, and parasites in both aquariums and ponds. They use a special fluorescent lamp that emits light in the UV wavelength and as aquarium or pond water is pumped through the UV housing it is exposed to this UV light. The DNA of any free-floating micro-organisms (bacteria, algae, and parasites) that are passed by the UV light is altered by the light and they are no longer able to multiply.

To select the proper size UV Sterilizer you will first need to decide what type of micro-organism (bacteria, algae, and parasites) you are trying to control.  This is important since the different micro-organisms need to be exposed to the UV light for different periods of time if their DNA is to be altered. For example the size of the UV Sterilizer you select to control bacteria or free-floating algae may not be effective against parasites. Larger organisms like parasites are more resistant to irradiation and require a longer UV exposure time.

The exposure time is determined by the wattage of the UV bulb being used and the flow rate through the UV housing ie. how strong the UV bulb is and how quickly the water passes by the UV bulb. Changing these factors will determine how effective the UV Sterilizer will be at controlling the bacteria, algae, or parasites you are targeting.

Fortunately most manufacturers make choosing the right size UV Sterilizer a fairly simple matter.  For example, Coralife the manufacturer of the popular line of TurboTwist UV Sterilizers includes this chart with their Turbo Twist 6X UV Sterilizer.

As you can see, to control parasites with the Turbo Twist 6X UV Sterilizer the flow rate should be no more than 110 gph but to control bacteria you can flow as much as 500 gph through the UV chamber.   Most manufacturers will publish a chart like this so be sure to review it as an aid in deciding which size UV you need.

One often overlooked consideration is how frequently (the turnover rate) your aquarium or pond water is cycled through the UV Sterilizer.  The turnover rate needs to be frequent enough to both keep up with the growth of the micro-organisms that you are trying to control and also frequent enough to ensure that the micro-organisums are actually being exposed to the UV light.  For green water you want to ensure that the volume of water in your system is being passed by the UV bulb every 2 or 3 hours.  For bacteria it should be passed by the UV bulb 1.5 times per hour and for parasites 3 to 4 times per hour.

See our blog post on how to Maintain your UV Sterilizer for information on changing your UV bulbs etc.