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Re: Aquatic Plants Digest V4 #410

> Date: Fri, 14 Jul 2000 09:24:51 -0400 (EDT)
> From: busko at stsci_edu (Ivo Busko)
> Subject: Ligthing
> Wright Huntley <huntley1 at home_com> wrote:
> <snip>
> > There is *no* effective attenuation of the photosynthetically active
> > spectrum in clear tanks that are less than a few *meters* deep. If you
> <snip>
> Not quite so. I converted the curves published at
> http://www.aquabotanic.com/paper2-6.html from their standard 1m depth to a
> "typical" aquarium depth of 16". For pure water, absorption at the blue end
> (400-500 nm) is effectively zero. But for all other cases: pure water at the
> red end (600-700 nm), and water with a reasonable amount of organics,
> absorption is in the range 20-50%. Significant IMO. Of course, this should
> affect mostly low lying plants. Stem plants and large swords for instance,
> should see less of the effect.

That was truly turbid water, when compared to our crystal-clear planted
aquaria. Try it yourself (which I did some years ago). You would be
disgusted at the cloudiness of a tank with those parameters.

With our usual filtering, our tanks would compare favorably with the *old*
Lake Tahoe for clarity. The pure water curve *is* more red-absorptive than I
expected. That, of course is the photosynthetically more active part of the
spectrum, too.

Nevertheless, I contend the *difference* in substrate-level available light
between an 18"-deep tank and a 24"-deep tank is essentially insignificant.

Hey Ivo! I think you have done a wonderful job of resurrecting the old
"blue-water-in-a-white-bucket" thread! <VBG>


PS Honest Cynthia, I was just kidding. ;-)
Wright Huntley, Fremont CA, USA, 510 494-8679  huntleyone at home dot com

           To err is human. To blame someone else is politics.
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