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re:dark period

>Stephen mentioned 4 (four ! ) dark days as an experiment.
>
>I am afraid your plants cannot sustain many of such dark
>periods....

It's a good idea to space them out pretty well.

>From Dennerle books I subtracted an other sort of "dark
>period":
>
>It's on a daily base:
> - mount a proper amount/sort of light
>then:
> - light on for 4 hours
> - light off for 2-4 hours (2 hrs. seems to be too little..)
> - light on for 6-8 hours
>Total:10-12 hours of light within a period of 12-16 hours.
>
>The more "basic" algae should not be able to adapt to this
>scheme; the aquatic plants should (It was tested!).
>
>Your plants should NOT react to this, or they might suffer
>too much (I think they did in the experiment you described)!
>
>Succes

Been there, tried it.  No effect on red algae.  In fact, the red algae seemed 
to do quite well, although the plants didn't seem to do quite as well.  I ran 
this way for about 8 months without extremely measurable effects.  

Based on information from this list and from other sources, along with my 
personal observations, I've found that some plants, particularly Rotala sp. 
fold up their leaves on a diurnal cycle.  The on-off-on cycle had a definite 
negative affect on these plants.

On the subject of several day dark periods, I wouldn't go off for 4 days and 
then on for 4 days,  I'd probably do something like off for 3-4 days and on for 
15 or so.  The interesting effect is that the algae doesn't grow at all during 
this time, and seems to even die back some, while the plants will "reach", 
producing several inches (for stem plants) of algae-free growth in their 
attempt to get more light.  When the lights come back on, this new growth is 
ready to go (more or less) and seems to take off much more quickly than the 
algae-covered plants were.  Yes, this isn't a solution to the algae itself, but 
it is a way for your plants to get a leg up on it, even Rotala sp.


David W. Webb
Enterprise Computing Provisioning
Texas Instruments Inc. Dallas, TX USA
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