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> Date: Fri, 14 Nov 1997 23:59:11 -0800
> From: Stephen Pushak <teban at powersonic_bc.ca>
Sorry for any perceived peevishness here. It's Monday.
> > It was great until we both decided it didn't work AND it killed off all
> > my Rotala macrandra. I was doing a 2 hour dark period (4 on, 2 off, 6
> > on). Good theory, bad practice. Sorry.
> Do you have any theory on what happened to the R mac George?
It didn't get enough light to grow very well and then it died.
Or perhaps it started to grow really well in the morning 4 hour period,
then started to convert nutrients to sugars during the dark period,
then the sugar got carmelized during the next 6 hour light period and
clogged the plant's arteries.
Not being a botanist leaves me ill prepared to speculate on theories.
> How did the plants die?
Slowly and painfully. Leaves dropped off. Stems rotted. New leaves
Again, I don't know because I didn't have an autopsy done. This was a
very trying period for us since we lost a VERY robust strain of R.mac
that we had been shipping all over the country with great success.
And you know how well R.mac ships...
> Could your dark period have upset a diurnal rhythym of the plant?
Either that or something else.
> Preserving a low level of lighting during the dark period might
> prevent this.
We had no way to do this on two of the tanks (their dual 2 bulb
fixtures were wired in parallel; something I'll NOT do again).
Another tank (with 2 175w MH and 2 40w Tritons on separate timers
suspended 14" above the tank) had what you describe but we didn't have
R.mac in that tank.
> This plant has fine roots which aren't well adapted to a low redox
> substrate however that probably wasn't the situation here.
I don't see the connection between a low redox substrate and a dark
period. Less oxygen from the roots? The tanks had heating cables.
Also, the R.mac roots weren't noticably finer than most other roots
such as R.indica, H.corymbosa, B.caroliniana, etc. The R.mac had
extremely robust and dense root structures that would regenerate in
two weeks after a top-off and replanting.
> If the overall light budget fell below the compensation threshold for
> Rotala macrandra, the plant could not produce sufficient sugars or
> energy reserves to sustain growth. This plant does require strong
That's my guess -- it didn't get enough light to grow very well and
then it died.
> From your comment, I gather that you weren't able to observe a
> difference in algae growth?
> As mentioned in the Krib article, green unicellular algae would be the
> most susceptible to this treatment.
We never had a problem with green water.
> Filamentous algaes survive dark periods quite well. What types of
> algae were you testing?
The only visible algaes we were concerned with were red brush algae
and that green cottonball-like stuff that grows around fine
structured plants like E.tenellus <insert scientific names here>.
Neither were visibly affected.
No scientific investigation was done.
Your results may vary.
George in Colorado where the artic front has finally left