I agree with liz regarding incandescent bulb life being shortened by
power cycling, though I always attributed it to the temperature cycling
(effectively causing the metal filament to fatigue). Cycling fluorescent
bulbs is also supposed to reduce their life expectancy, but I don't know
the mechanism. The ballasts will also be a consideration. I'd contact
the manufacturer to see what they recommend for maximum life. One of the
fluorescent manufacturers (Phillips, GE etc) might have data on their
websites as well.

note to Donald, ..turnover/..html... book-marked )
NetMax

"liz bolyard-mick" wrote in
message ...
I may be wrong, but I believe that only incandescent bulb life is
shortened
by turning it off and on due to the surge of electricity passing
through the
filament. This surge weakens the filament by vaporizing pieces of the
filament. During normal usage, samll pieces of the filament detatch and
float freely in the bulb, but they are drawn back to the filament to
settle
on it. It is the vaporization of the small pieces of the filament that
shortens the life of an incandescent bulb. I don't believe the same is
true
for any flourescing type lamp, but I don't know as much about those
types.

"Bruce Geist" wrote in message
...
Basically, you are only culling the population of algae spores and
bacteria
to a level, presumably, that is more like an open stream or lake.
All
tank
water is never sterile at any one moment in time, since algae and
bacteria
are constantly re-growing.

To control a specific organism or class of organisms, use the lowest
lethal
dose for that organism or class of organism, meaning you turn your
flow
rate
up so that water passing though is exposed to the right level of
radiation,
and no more. That way, you are killing algae at the quickest
possible
rate. The flow rate is effectively your control on the dosage you
are
delivering. So, if algae is your target, I'd turn your flow rate to
about
200 gallons per hour. This will deliver (I am estimating here) about
50,000
micro watt-seconds / cm^2 of radiation to the water passing through
your
sterilizer.

Here is the shaky part; I am not sure exactly what dose will kill all
algae.
So be aware, I am making a swag here. I do know that Chlorella
Vulgaris,
a
kind of algae, is killed by 45,000 micro watt-seconds / cm^2 of UV.
Therefore, I am recommending a flow rate that I believe will cause
your
36
watt sterilizer to deliver the 50 K micro watt-seconds / cm^2 dosage.
I
do
not actually have intensity data for your particular sterilizer,
though I
have requested it from the manufacturer (because I am doing some
mathematical modeling for an article I am writing..) I have
intensity
data
for a 30 and 64 watt UV set-up, so I am interpolating a result here.
However, the dosage estimate is really an estimate! Sorry I cannot
be
more
precise.

Now its your choice whether to leave on the sterilizer or cycle it.
I do
not believe the statement that cycling a UV lamp shortens its life
significantly. Maybe it does, but I find it hard to believe. In
fact,
the
lamp manufacturer defines its useful life in terms of hours on, not
number
of cycles. If you leave the thing on all the time, the lamp will
last
about
6 months. If you use it only during the day, my expectation is that
it
will
last a year. Since your target is algae, maybe its enough to
sterilize
when
the algae is multiplying during your tank's lighted period.

Do some experiments, and see if you perceive a difference in water
quality
and/or algae proliferation when cycling and not cycling. And then
let me
know what you conclude! I'd really like to know what your experience
turns
out to be...

-Bruce

http://www.wideopenwest.com/~brucegeist

"Christopher" wrote in message
rthlink.net...
Thats a very detailed explanation, THANKS!
have a couple questions though:
if the primary reason I'm using the steralizer is to kill algae
spores
so
my
tank stays clean is it smart to only have the steralizer running
for X
hours
a day? Cant the spores be released and land and settle on the
glass and
leaves during the off period? My second question is how much life
of
the
bulb is saved when you run it for 8 hours a day? I know that the
turning
on
of the bulb takes away from bulb life, but would the fact that its
only
run
for 1/3 of the time save bulb life in the long term? I am
concerned
since
36W PC florescents are $50 (not exactly cheap)

"Bruce Geist" wrote in message
...

Actually, the 9.2 factor will give you 99.99 % throughput through
the
sterilizer. To get 99.9% throughput, the factor is 6.9.
See http://www.wideopenwest.com/~brucege...ver/index.html
for details.

One strategy is to set the flow rate through the sterilizer so
that
one
pass
kills target organisms you wish to kill. If you set the flow
rate
slow
enough that everything you want to kill is killed, then run your
sterilizer
long enough to "turnover" the tank water once or twice a day,
and then shut the sterilizer off.

Basically, the more slowly you put water through the sterilizer,
the
more
UV
exposure every bit of water passing through the sterilizer
receives.
If
you have a 36 watt sterilizer with about a 3 inch diameter
chamber for
the
water, and your flow rate is about 100 gallons per hour, then you
are
probably irradiating your water at about a 100 microwatt-seconds
dose,
which
is
enough to kill most bacteria, algae, and many protozoa. (This is
only
a
crude estimate; I am working on developing some assessment tools
on my
website which will provide more specific advice..) If you are
using a
lower
wattage sterilizer, or a lower diameter sterilizer, then your
flow
rate
will
need to be lower still to achieve the same dose.

In the article I wrote cited above, I show that when you have run
99.9%
of
the water through the sterilizer at least one time, in actuality
99.2%
of
water has passed through 2 or more times, and 96.8% will have
passed
through
the sterilizer 3 or more times! I recommend 6.9*(tank size in
gallons)/(flow rate in gallons) to be your target turnover time.
If
your
flow rate is chosen with some care, you need not run your
sterilizer
all
the time. You will save bulb life by running your sterilizer
through
only
one or two
turn-over intervals per day.

I hope you enjoy the article on turnover time; this is the first
time
I
have
published the web address. Remember that you can skip to the
conclusion
and get the formula to use. I am in process of collecting data
for a
suite
of articles on the topic UV sterilizers. Be watching this news
group
or
my
web site; I am waiting on data from a manufacturer. -Bruce Geist

"Christopher" wrote in message
rthlink.net...
is it wise to run the UV steralizer 24 hours a day? assuming
that
you
only
desire a 99.9% steralization rate you don't have to run the
steralizer
that
much (depending upon gph through the steralizer and tank size).
I've
read:

9.2 * (tank size / gph through steralizer) = hours a day UV
steralizer
must
be on to attain 99.9% steralization rate (assuming uniform
mixing).
This
said my calculation is at most 7 hours a day, should I just run
it
for
8
hours a day and save my bulb life and power bill?

Should I run it 24 hours a day to achieve 99.999% steralization
or
for
8
hours a day?

I know for most people it isn't a big deal but I don't like algae
in my tank and for me...

It's not just you. Most people hate algae in the tank.

That way I can run the lights more than 8 hours a day
and I don't have to spend an hour scraping the sides of the tank every other
week.

Most people don't have UV sterilizers and don't have to spend an hour scraping
the tank, either. If your tank is in balance, your algae problems should be
minimal.

And you should have your lights on more than eight hours a day. Aquarium
plants generally need a 12 hour day. You should not go below 10 hours. Too
short a photo period can actually help algae, since the plants won't be growing
as well as they should.



Leigh

http://www.fortunecity.com/lavender/halloween/881/

well I'm up to 12 hours of full light and 30 minutes of sunrise and 30
minutes of sunset

full light is 120W (80W power-glo 40W actinic 03)
sunrise/sunset is 40W actinic 03
all over a 125g

"LeighMo" wrote in message
...
I know for most people it isn't a big deal but I don't like algae
in my tank and for me...

It's not just you. Most people hate algae in the tank.

That way I can run the lights more than 8 hours a day
and I don't have to spend an hour scraping the sides of the tank every
other
week.

Most people don't have UV sterilizers and don't have to spend an hour
scraping
the tank, either. If your tank is in balance, your algae problems should
be
minimal.

And you should have your lights on more than eight hours a day. Aquarium
plants generally need a 12 hour day. You should not go below 10 hours.
Too
short a photo period can actually help algae, since the plants won't be
growing
as well as they should.



Leigh

http://www.fortunecity.com/lavender/halloween/881/

"Christopher"

UV's have a couple of planted tank uses.
One is for green water
The other is for the 24 hour period after a water change.
So you will only need to use it once a week after the 50% water
change.
They do no good after this period.

I don't use them on my tanks personally. Don't need too.

Try a credit card for getting algae off the glass.
I think you'll find this is the best use for a credit card rather than
it's intended purpose.

If you address the CO2/nutrients, cleaning the glass is seldom an
issue.

Regards,
Tom Barr

The other is for the 24 hour period after a water change.

Why for a 24 hour period after a water change? (Just curious -- I've never
heard that one before.)

I originally got my UV sterilizer to prevent ich. I just couldn't face
prophylactic treatment with chemicals for a 75 gallon tank, over the long weeks
of stocking using Chuck's "no-cycle" setup.

I've left it on since, mainly to knock bacteria levels down closer to the
natural levels you find in lakes and streams, but I'm thinking of turning it
off. It's one more powerhead to clean, and I'm lazy!


Leigh

http://www.fortunecity.com/lavender/halloween/881/