The Use of Ultra Violet (UV) Radiation in Aquaria systems
An article by Andreas Iliopoulos
Because quite a lot of debate exists considering the use of ultra violet radiation in aquatic systems, it is useful to comment on the safe and efficient way of its use.
One UV lamp is not a panacea if it is not used correctly based on the exact specifications of the manufacturer and also based on the intended use (even if this is the prevention of a disease or during the healing process). The ultimate target of UV radiation is the killing of specific aquatic pathogens. Thus, the UV lamps can be used for the prevention and/or treatment of bacterial infections, several kinds of fungal and viral infections as well as infections caused by parasites or even algae.
Their power is measured in μWatts (microWatts, one microWatt = one millionth of a Watt) but this is just one of the parameters that should be considered. Someone who is aiming at a safe and efficient use of UV radiation should also check the amount of the passing water (water flow) that must be achieved, the desired water volume that must be treated and the sort of pathogens that are to be fought.
Here, I present a list (*) of pathogens, along with the respective killing doses for them. Anyone can use this list to calculate the wattage and the flow rate which is needed to treat a specific problem, disease or pest in a system.
One must also know that wattage of the UV lamps is decreased in time and they should be normally replaced every six months (at least), so the wattage declared by the manufacturer will be constantly applied on the passing water thus rendering the UV lamp effective against the pathogens. Switching the UV lamp on and off (as with all lamps) is the main reason for this short period of useful life time.
ATTENTION: UV radiation can cause blindness (destroys the retina), so be sure that the lamps you use are properly isolated inside protective shields (specially made chambers for UV lamps) and try not to stare at a switched on lamp with naked eyes. Glass - strange as it may sound - blocks UV radiation.
NOTE: μW•s/cm² = microWatts x seconds per square centimeter. The average UV lamp with a wattage of eight Watts (8 W), measure about 11½ “ (about 30 cm) and have an output of 12.500 μW•s/cm². This means that if a fungus is our target, it should remain exposed to its radiation for at least 4 seconds in order to be killed, hence the need to calculate the flow rate.
(*) The list was obtained by RAINBOW-LIFEGUARD Aquatics.