Re: [Killietalk] UV irradiation ... WAS ... Flow thru systems

[LeeH920226 at aol_com]

I have no evidence that immunity of fishes is built up by exposure to 
pathogens. I also have no evidence that susceptibility is enhanced by lack of 
challenges to the immune system. I do know from personal experience that fish that 
are stressed by poor water quality are more likely to become diseased. In my 
once through system the tap water is relatively free of pathogens since it was 
chlorinated by the water company. Certainly with the addition of fish, plants, 
live and frozen foods, etc., there are many microorganisms present. I think 
they are beneficial when balanced (good vs. bad). I also believe that heredity, 
diet and exercise are the most important contributors to a healthy existence 
for humans. Extrapolating to fish would suggest that a water changing system, 
with or without UV would be secondary to the overall health and vigor of the 
fishes. But, if it reduces stress from water quality deterioration, it should be 
beneficial. I am not sure where exercise fits into the fish except for chasing 
live foods or chasing/escaping from amorous tankmates. Now, what is it that 
improves the vigor of fish in the once through water system? I believe it is 
the "flushing the toilet" analogy that someone on this list (possibly Charles 
Harrison) suggested. The closest thing in terms of results is the Lava Rock 
DeBruyn filter which I have also had very good experience with.

Lee Harper
Media, PA

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