The terminology can be confusing, but whether you call them a UV filter, UV light, uv sterilizer, Ultraviolet light, clarifier or UV unit, you are talking about the same thing. They are all the same type of UV filter. There is a lot of confusion besides just the name of the uv filters as well. Some manufactures rate the power, or radiation, that their ultraviolet light produces at the bulb, others rate the power of their UV pond filter at the outer wall of the vessel, still others rate their sterilizers radiation production at the end of bulb life.
So how do we sort out this confusion? First, get the facts so we are not comparing apples to oranges. Fish, whether koi or goldfish, have fewer health issues in a system that has an adequate ultraviolet light installed. Over crowding is pretty common in most hobbyists ponds and especially in dealers sales tanks, kind of like a crowded waiting room at the doctors office. Over crowded systems are perfect for bacterial gill disease and other disorders to take hold and reducing the bacteria count in a pond can significantly reduce health issues. In my opinion adding an ultraviolet unit to your pond can be one of the more important things you can do in terms of keeping your fish healthier. Sadly, they are only being used to kill algae, however, if the flow rate of the water passing through the light is correct they WILL kill bacteria and many parasites that attack our fish (all of which have a free swimming stage), including eggs. So, if the unit is large enough to produce the required dosage given the flow rate of your pump (not the size of your pond) you will enjoy fish with fewer health issues.
Most of the units sold for ponds are capable of producing 30,000 microwatt seconds per square centimeter, or more, at the outside casing, IF the flow rate is correct. This is more than enough to kill most pathogens. Even those larger pathogens that are not killed have probably been damaged to the point that they will not reproduce. Ultraviolet radiation treatment is unique in its mode of action, in that it does not necessarily kill the target microorganism. Ultraviolet radiation alters the DNA strands so that the micro-organism is sterilized, thus inactivating the pathogen so that it cannot proliferate and cause disease. A bug that can't reproduce simply dies. Germicidal ultraviolet light is considered lethal for most micro- organisms, including bacteria, fungal spores, viruses, protozoa, nematode eggs and algae. That part of the ultraviolet light spectrum known to kill or deactivate most pathogens is between 100-280 nanometers, which is just below visible light to soft X-ray. This is the operating range of units that should be used on ponds and is known as UVC as opposed to UVA or UVB and requires the use of a low pressure bulb. While pathogenic bacteria are the easiest group to treat, and differ the least in the amount of radiation required, viruses are more resistant and variable in the amount of radiation needed to neutralize them.
Points to ponder about ultraviolet Pond sterilizers
- An ultraviolet unit should be run 24/7 because bacteria is always present.
- Ultraviolet filters are most effective if the water is clear.
- An ultraviolet unit is most effective if the light bulb is new, or replaced regularly (at least every 12 months).
- Ulatraviolet units are most effective if the light only has to penetrate less than one inch of water.
- Effectiveness of an ultraviolet unit can be hindered if the water passes to fast past the bulb.
- Ultraviolet units are most effective if the exposure time of the water to the light is longer than one second.
- The effectiveness of light can be hindered if there is light blockage, i.e. a salt encrusted bulb.
- Ultraviolet lights can help to prevent future water borne pathogen reoccurrences, once the initial problem as been completely eradicated from the pond.
- The pond unit should never be run when treating with any drugs or medications.
- The pond light can also alter the structure of some dissolved chemical compounds.
- The pond light can be damaging to the human eye, so DO NOT look into the bulb.
- Always unplug the pond light when working on it to prevent possible shock if it breaks or gets wet.