[slief]

Originally Posted by richiero

i feel there is a lot of good info on that web site, on aqua uv's web site is says A UV Sterilizer is a proven method to eradicate bacteria, viruses and protozoa. why do they false advertise? and how could they?

It's not that they false advertise. UV's can certainly play a helpful role in those areas but in order for anything to be eradicated, it has to be suspended in the water column and would have to pass through the UV sterilizer at a proper flow rate. In a reef tank where there are rocks, sand, corals, fish etc, the UV is more of a tool to help maintain a cleaner and more healthy environment but it's impossible to expect all water with those forms of life to pass through the UV as those forms of life will reside not only in the water column but on the fish, in the sand, within the rocks etc.

Also keep in mind that much of what they are talking about is based on a fish only system in which the flow rates through the UV are at the low end for absolute sterilization or even in water purification systems for drinking water. In a reef tank, the low flow rates required to kill protozoans and other things, will also kill copepods and other life forms that we strive to maintain. As such, there is a trade off and many of us that use UV's in our reef tanks tend to run them at the higher flow rates in an effort to use them more for polishing water while also not killing off our pod population. Even so, the UV will have some impact on pods as well despite the high flow rates. Reality is that if we maintain a stable environment in our tank and employ good quarantine habits with preventative treatment, much of what you are worried about is really a non issue. A UV at a high flow rate will still help control bacterial blooms and can render many parasites sterile so they can't reproduce. A UV at the higher flow rates will also help maintain pristine water clarity, It's just that in a reef, you would likely want a higher flow rate through the UV so that you are not killing everything that passes through it and even at lower flow rates, you have to have realistic expectations.

That said, as I mentioned, a UV will only kill what passes through it. Many parasites reside on a fish or elsewhere in our tanks where they continue to reproduce and may never come in contact with the UV filter. Bacterial infections in fish will remain in the fish and a UV filter won't do any good in those instances as well. Same goes with Ich which has different stages in it's cycle. One is what we see on the fish in the form of the white spots. It then falls off at which point it is in the water column for a very short amount of time before it settles into the substrate until the cycle repeats itself. As such, the UV filter will not eradicate it as a very small percentage of ich in it's free floating stage will even make it though the UV. The UV will (depending on the flow rate) kill some of it but not all of it.

As such, a UV filter in an aquarium can play a role in a cleaner system that is less likely to have parasitic or bacterial issues but it is in no way an end all be all for those problems unlike a sterile and contained environment such as a water filtration plant where all water is continually filtered though the UV. In that case, the impact of the UV filter is much greater and the results and impact are obviously more definitive.