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[APD] Siesta to prevent algae?


I just bought a German book published by Dennerle. (As
far as I know, an English version is not available.) The title
translates as "System for Fascinating Aquariums". The book
has a quite a bit to say about preventing algae. One of the
suggestions is one that I have not come across before, and I'd
be interested whether anyone has any comments. Here is the
relevant passage:

"Our recommendation [to reduce algae growth]:
 Reduce the lighting duration from 12 to 10, 9, or 8 hours. Or,
 even better, allow your plants and fish a `siesta'. The following
 rhythm has proven itself: 4-5 hours light in the morning, then a
 a dark period of 2-4 hours, followed by 4-7 hours of light.

 During the dark period, the tank should not be entirely dark, but
 receive diffuse light from a window at 2-3 meters distance or from
 a light bulb at 1-2 meters distance. The light periods should always
 last for at least 4  hours because shorter light periods are not registered
 by many plants. Contrary to popular opinion, we have not noticed any
 negative effects of this lighting rhythm on either fish or plants -- 
 because significant light reduction is frequent in the tropics, for example
 due to thunderstorms.

 Algae obviously dislike the `siesta'. It is currently unknown whether
 this is due to the [in evolutionary terms] `primitive' algae being less
 adaptable than the`modern' plants, or whether this is due to an
 improved oxidation/reduction balance. At any rate, the `siesta' is
 surprisingly effective against algae."

I was curious as to whether anyone has tried this and could pass on
any comments. Personally, I don't see how it would make a difference --
when I turn on the lights, I can watch my plants producing oxygen bubbles
within a few minutes, and when I turn the lights off, I see the bubbles
disappear within a few minutes; presumably, algae would do exactly the
same thing, that is, start photosynthesis as soon as light is available, and
stop it again when the light disappears. So, I don't see how having a
dark period in the middle of the day would help to reduce algae --
the total lighting period and intensity is the same, so I'd expect the
same total growth. But maybe I'm missing something more subtle?



Michi Henning              Ph: +61 4 1118-2700
ZeroC, Inc.                http://www.zeroc.com

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