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[APD] Re: Aquatic-Plants Digest, Vol 14, Issue 45

>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:

I gave a critique of their suggestions on APD, and AQ.
A rather blistering critque...
It was from their Englisg version site.
You can look it up on those forums.

>"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.

Well, my suggestion is to improve the plant growth.
Algae and plants both have choloroplast, why would this do anything?

I think what is occuring is that the CO2 is mildly insufficent. Turning off the lights stops the CO2 uptake.
This gives the CO2 system and chance to catch up.

Unless they do a control and make sure other parameter are independent the lighting, how will you know?
I suppose just try it and see but you need to be sure that the light in and of itself is the causative variable.
> "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 -- 
>  presumably
> because significant light reduction is frequent in the tropics, for example
> due to thunderstorms."

And algae are also sujected to this same environment!
We have algae in the northern regions, in deserts, etc, they still grow, I don't buy the tropics thunderstorm arguement for a second.

> "Algae obviously dislike the `siesta'."

It's not so obvious to me. 

> 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."

If you assume it works.
It does not hurt anything really so folks can try it out, no harm done.
Cables the same deal.
But they cost$.

>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?

No, you are a right on.
Try it and see, it doesn no harm.
If it does work, check your CO2 carefully over the same time peroid.

For CO2 enrichement:
90-95% of algae problems can be traced to CO2, the other 7-4% are NO3 related.

If a peroid of dark helps, then a blackout will do the most harm to algae vs plants.
Generally less light is better also.
This also places less demand on CO2 supply.

Tom Barr


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