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Pet Product News Editorial Blog:

Thursday, August 13, 2009

To UV or Not to UV

By Patrick Donston

Store Owner, Absolutely Fish


Ultraviolet sterilization is the most important part of a marine system when it comes to parasitic disease and bacteria control. I've had conversations with shop owners who don't use them, use them incorrectly or believe they do more harm than good. I think maybe they don't understand them or know how to use them properly.
When choosing a UV system I recommend oversizing. Keep in mind: The effective qualities of UV are determined by the power of the bulb, distance of the bulb from the water and the flow-rate past the bulb. Most bacteria and parasites that are within 2cm from the lamps can be irradiated. The rating used is measured in microwatts x seconds/cm3.
Most sources state 15,000 to 30,000 microwatts seconds/cm3 is needed to irradiate bacteria, and up to 90,000 are required for protozoa. In other words, the intensity and exposure time are central to controlling pathogens in marine systems. There are many arguments over which company manufactures the best germicidal lamps, as well as disagreements over how much water to flow through a particular UV system. With all of this said, how do we know what to do?
I emphasize doing your research and using a UV manufacturer with experience in building commercial UVs for aquarium or aquaculture facilities--their ratings are usually studied and somewhat proven. Although I have never performed a scientific study upon the pathogens UVs remove from our marine systems, I can notate differences in the health of our fishes when using different styles, intensities and flow-rates. We start with 1 watt per 5 to 10 gallons of system water and a flow rate of 10 to 15 gallons per hour per watt of sterilizer. Of course, we take into consideration manufacturer specs and consult with the company before setting up. I've found stainless units have added value as they last much longer and are more durable in a commercial setting.
It is one thing to have a UV system, but another to have it running properly. Pre-filtering the water for particles, having a protein skimmer for dissolved organics, routinely cleaning of the sleeve, slowing the flow-rate and oversizing the unit will increase the effectiveness of any UV system.
A few other tips that may help when using UV on your systems:

  • Always valve your UV hoses. Slower flow rates increase the dwell time and can be advantageous when disease inhabits systems or when the germicidal lamp exceeds 40% percent of life capacity.
  • Mount UVs vertical not horizontal. Water will not completely fill a horizontal tube, preventing the system from sterilizing to its maximum capacity.
  • Piggyback UVs and alternate changing the bulbs every 6 months. That way there will be one fresh bulb and one at 50-percent capacity most of the time.
  • Keep good records and check your UVs once a week. Remember: Bulbs should be changed approximately once a year and sleeves cleaned twice a year (more for reef systems). If written down, you're more likely to keep up with routine maintenance.

I believe in UVs. They work if you choose the right size, run them properly and keep up with the maintenance. Most notable aquatics facilities use them and with good reason. They keep disease down and fish healthy.

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