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Re: Reverse Photoperiod


    If what you mean by 'reverse photoperiod' is to have lights on for algae
scrubbers at night while the main tank is lighted during the day, I think I know the
answer.  It has nothing to do with nitrogen uptake.  A marine hobbyist I know uses
this system to reduce pH and alkalinity swings on his reef tank.  Heavy
photosynthesis can cause alkalinity drops and pH increases during the day.  If you
have an algae scrubber hooked up to the main tank that is going through this cycle at
the same time, you would greatly accentuate the pH/alkalinity changes.  Solution:
Turn the lights on for the algae scrubber at night only.  The pH and alkalinity stay
much more constant, because the two cycles going at different times sort of cancel
each other out.  Its a terrific idea for stabilizing pH and alkalinity in marine
tanks with their delicate organisms.
    However, I suspect that it would not have much application to planted tanks.
Most freshwater plants are used to pH and alkalinity swings.

Diana Walstad

> ------------------------------
> Date: Fri, 14 Apr 2000 22:05:21 -0800
> From: "Thomas Barr" <tcbiii at earthlink_net>
> Subject: Reverse photoperiod filtration?
> If plants can use Nitrogen at night as suggested by Roger Miller then the
> bacteria can also because most of the responsible bugs(bacteria) don't need
> the light to use nitrogen.
> So this idea of Reverse Photoperiod cycling shouldn't work really, correct?
> Perhaps some as the plants get towards the end of the dark period? But the
> bacteria will work all the time.
>  Do algae use N at night also like the bacteria and plants? To what extent?
> If they do, what the heck is this notion of Reverse Photo period for
> filtration? If the nitrogen is being used up by both the plants and the
> bacteria and maybe algae then why do these companies promote the Reverse
> photo period idea as being an some sort of advantage when using
> scrubbers/filters for N removal?
> Regards,
> Tom Barr
> ------------------------------