Re: [RML] UV sterilizers

Craig Bingman (cbingman at netcom.com)
Sun, 31 Aug 1997 00:43:33 -0700 (PDT)

On Sat, 30 Aug 1997, Jim Priest wrote:

> Hey everyone...
>
> Does anyone out there use UV sterilizers. Somebody (who hasn't used
> them) suggested I try them out. Seems like I heard or read somewhere
> they weren't compatable with live planted tanks? You would think by
> reading the ads for them that they eliminate bacterial and viral causes
> of disease...but if this were true, you would think everybody and their
> brother would have them. They aren't that terribly expensive. Does
> anyone have the scoop on them?

I wear a UV sterilizer in my boxer shorts. I find that it eliminates
bacterial and viral disease, as well as being the ultimate cure for
largemouth bass bite marks.

The only problems that I have with that are a terribly sunburned willy,
and that I keep hitting the end of my extension cord.

I guess that you want the serious answer?

UV is a complicated subject.

I guess the history of the freshwater applications of UV are to control
disease and microalgae blooms in the water column. It can help with
both, but I personally regard it as a very technological fix, and if I
can get by without them, I try to do so.

The history of UV in saltwater is similar, except that the microalgae
angle isn't often invoked. We have foam fractionators in marine systems
that rip microalgae out of the water column, so they aren't an issue
(except benthic species.) People often roll out the UV "cure" for
diseases of saltwater fish.

So we have a consistent theme... disease control and UV. There is no
doubt that 254 nm radiation from a low-pressure Hg lamp will kill pretty
much any small organism, given an adequate dose. Caveats are that the
organism has to go through the UV unit. The problem with that is that if
the fish are sick, they have pathogens on them.

I'm most definitely a product of the 20th century, and am a biochemist on
top of that, so I do believe in primary bacterial pathogens, etc. A
sufficient dose of pathogenic bacteria can cause disease in fish.
However, pathogenic bacteria are everywhere, and fish aren't dropping
like DDT poisoned flies, so what gives? Healthy, relatively non-stressed
fish can fight off many bacterial and viral diseases. We should strive
to have non-stressed fish. The caveat there is that we hold fish in very
high population densities in aquaria, so once a disease gets rolling, it
can progress to the point where otherwise healthy fish are overwhelmed.

I have a very nice, totally unused 40 watt UV unit. If you pick it up,
I'll sell it to you for $200.

UV and freshwater plants. 254 nm radiation is sufficiently energetic to
pump redox chemistry. Iron, and in particular, iron-organic complexes
absorb strongly at 254 nm. I believe that the feeling that UV is
incompatible with planted tanks revolves around this issue. Iron should
be rapidly lost from the water as it is converted into insoluble Fe+3
forms by the UV.

Best wishes,

Craig