# Re: [APD] Re: Amano's AGA demo -- or - a little off the sides but not too much off the top

```--- Ann Viverette <annv777 at houston_rr.com> wrote:

>> > Scott H.
>
> I know that our own dear Eric once wrote a strategy for
> calculating the
> lighting times that would be needed for various sorts of
> tanks; that is
> slow, moderate, and fast growth tanks. It calculates a
> watt-hrs required
> which I used  to calculate the high vs. low light periods
> in my 59 gallon
> tank. My tank has a 4x55 solar hood with dual switches
> and I was pretty sure
> that running it at 3.6wpg all day long would be too much
> work.
>
> I don't have a link to Eric's original post and when I
> recently tried to
> locate it I failed, but my notes for the calculations I
> did for my tank
> (going from 1.8 to 3.6 wpg mid-day) show that the volume
> of the tank in
> cubic inches was multiplied by a factor of 0.18 for
> moderate bright (or 0.27
> for bright) to give a watt-hrs needed. This was
> distributed over an 11 or 12
> hour period with the excess doubled up at mid-day. In my
> tank, this resulted
> in 2x55 watts running from 8AM to 7PM, with the
> additional 2x55 watts on
> from 10AM to 1PM. I have no idea what the factors
> represent, but this
> strategy seems to work OK.
>
> I do note that If I keep the ferts going correctly,
> dosing several times
> during the week instead of just once a week, the tank
> will bubble all during
> the photoperiod, not just at midday. Perhaps the 1.8wpg
> is still pretty high
> since the lights are flat against the glass top. The
> tanks Amano uses seem
> to all have the lights placed far away and no one seems
> to figure that loss
> due to distance into the wpg used on a tank (intensity
> ought to decline as
> distance squared, no?)

For a point source of light (such as an MH bulb), above the
water, that is the correct formula. For a line source of
light (like a fluorescent tube) the loss is less over
distance so long as you are measuring somewhere below the
middle and not under the ends of the tubes. If you are
measuring under the ends of thetubes, the loss is about
half way between what it would be under the middle of a
tube and under a point source.

And all this changes once you get down into the glass-panel
box, because reflections off of the glass panels put back
some of the light that would otherwise be lost to spread.

One of the things that interests me about differential
lighting is that the appearance of the tank will be diff at
diff times during the lighting period. I like that -- I
like seeing a tank under diff lighting amounts, all the way
from high lighting down to a few well-placed LEDs. For me,
it makes for that much more to see -- and not just in the
mere appearance of plants and shadows but also the behavior
of some fish. I'm not even that fond of having even
lighting over my entire tank -- although this is less
relevent with smaller tanks than larger ones.

Things are rarely even, mown into mounds, grouped neatly by
species, or always illuminated the same way, in nature and
I like the variety. Of course, some would say that I'm just
a sloppy gardener ;-)

And wandering a bit down the same aesthetic, now I wonder,
I've seen fog in paludaria, but how many do rain? Rain
doesn't look like much on a submersed garden but over a
paludarium . . .

Good luck, good fun,
Scott H.

=====
--- Christel Kassellman is returning to America! ---
The Northeast Council of Aquarium Societies will feature Christel, author of _Aquarium Plants_, among its speakers at its 30th Annual Convention. It's the longest running consecutive general tropical fish convention in the country and one of the most fun to attend.

March 18-20, 2005
Marriott Hotel, Farmington, CT
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