• Danger of UV Sterilizers to copepods in reef aquariums.

Have you had any personal experience with using UV Sterilizers in your aquarium?
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As for a UV sterilizer depleting needed nutrients and killing off beneficial crustaceans, all of that really depends on how your UV unit is plumbed in with your aquarium. If you are using a refugium and want to be certain that all of the amphipods and copepods that spill out into the aquarium are not killed, then be sure your UV is on its own pump and not returning water to the aquarium using the same line as the refugium. Whenever you dose your aquarium with certain products, turn off the UV sterilizer for eight to 24 hours to make certain the products are given time to work. Ultraviolet light not only kills bacteria and algae but it can also break up chemical compounds rendering them useless.
Also, it is recommended to install the UV sterilizer when the aquarium is cycled.
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With a complex chamber that forces water to pass by the UV light multiple times, this highly effective and efficient UV sterilizer keeps water clean and clear. Suitable for both freshwater and saltwater aquariums. Simply cut the stepped hose adapters to the appropriate tubing size, connect hoses, add hose clamps and plug in. Use a water pump that does not exceed the gallons per hour (GPH) rated for the corresponding Eliminator In-Line UV Sterilizer below. For a  up to date article about aquarium and pond uv sterilization, please visit this site:
Photo provided by FlickrI continue to follow the threads on forums, aquarium articles, and blogs about UV Sterilization.
Photo provided by FlickrAquarium-Pond UV Sterilizer History (from my professional perspective dating back to 1978)
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The aquarium UV Sterilizer is a water filtration device that uses an ultraviolet light bulb to kill microscopic organisms that are free floating in the water. Parasites, viruses, algae and bacteria (good and bad) are the type of things that are "killed" after passing through the ultraviolet sterilizing unit. UV sterilizer devices can be used on swimming pools, in liquid factories (think beer) and in the home aquarium using an aquarium UV sterilizer. Some large water purification centers employ some sort of UV sterilization on the outgoing water. These sterilizer units are also sometimes used in outdoor ponds to help control algae growth and they seem to do a decent job.Aqua Ultraviolet’s UV Sterilizers have been used by public aquariums, importers and hobbyists alike to control bacteria, protozoa and parasites, reducing the spread of fish disease. In a confined environment like an aquarium UV and filtration are essential. When using a UV Sterilizer in a home aquarium, the UV unit should be placed last in the filtration line. You want to first filter the aquarium water through your and then run the water through the UV device before returning the water to your fish tank. By first removing the solids in the aquarium water with your mechanical filter (canister filter, etc), you are helping your UV unit to attain maximum operational efficiency.Much of this information is courtesy of:

This is probably the most in depth and accurate article on the subject of aquarium UV sterilizer use I have read anywhere.
The author of the above article is one of the leading authorities on this subject with a considerable amount of hands on experience using and even designing true UV Sterilizers as well as UV Clarifiers which are commonly marketed as UV Sterilizers.

Readers will also note that it is often updated too, making for the most current information.The basic criteria for a sound UV sterilizer design revolves around a careful selection of lamp type, lamp length, lamp position, and body diameter. These factors, together with the intended water flow rate, percent transmittance of the water to be treated, and UV dose rate needed to destroy the targeted microorganism or pathogen, should be the basis of your decision when purchasing a unit for your pond or aquarium.As any responsible fish owner would do, you should first do a little research on what type of UV sterilizer would be a best match for your aquarium.