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Re: [APD] UV Question

The wattage of the bulb, as an ersatz measurement of the
amount of useful UV light, is important as well as the flow
rate of the water through the lamp.

Water flow determines how often all the water in the
aquarium gets passed through the UV.  But if the flow is
too fast, then the amount of time that any one thing is
exposed to the UV light will be too short.

Generally, bigger UVs are needed for bigger tanks so that
they can handle larger water flows.

But you might be surprised at how small a UV will prove
useful. I tend to buy larger than necessary and change the
bulbs less often.  Of coursem if you consider doing the
same, you'll have to price the replacement bulbs and see
whether that's economical for you.  Only a small percentage
of a UV bulb's output is in the useful UV range and the
amount of UV light decreases with the age of the bulb. 
Some manufacturers recommend replacement after 6 months of
continuous use, others after as much as 18 months -- so
that's something else to take into account.

The manufacturers all have recommended sizes of aquarium
for each of their given products.  If you look them up on
their web sites, you'll find that the recommended maximum
aquarium size for a given size UV will vary greatly.  This
is partly due to design differences, different assumptions
about flow rates, different assumptions about UV output due
to age (some ratings are based on a new bulb, some on 60%
life, etc.) and some are based on lethality only for algae,
which requires a much smaller exposure than protozoa.

Also, some use the older design, straight UV bulbs while
some use the newer Power Compact format which are a bit
more energy efficient.

If you're considering a UV, the prices also vary widely.
Lat week I found a popular model selling for as little as
about $62 and as much as $128, quite a spread! The best
prices I have found recently are at Bigalsonline.com but
shopping around on your own is always a good idea.  Hey, if
you find better prices, let us know!

For a 30 gallon tank, 8 or 9 watts should plenty.
The products you mention are very well built but a but
pricey, imo. Consider also the Custom Sealife, Tetra's
unit, and the relatively new Coralife models.

Scott H.

--- Seweryn Bialasiewicz <s_bialasiewicz at hotmail_com>
> Is the wattage on the bulb relevant to only the velocity
> of water which is 
> pumped through it? Or is there more significance to it,
> like a lower wattage 
> not being able to kill certain kinds of bacteria, etc...
> So far I have found a coupole of brands, and was
> wondering if people had any 
> good/bad experiences with them, or suggestions on what
> brand to get, or what 
> to look for when shopping for one.
> So far:
> Aqua Pro UV Stereliser series
> or
> Rainbow Lifeguard series
> - any of these good?

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