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RE: Barley Straw, H2O2, Redox

I want to preface this post with a clear statement that I don't think that
_any_ of this hi tech fiddling is necessary to maintain a beautiful and
algae free planted aquarium....

Dwight wrote:

> Well, well... the plot thickens... a Barley Straw reactor form Dupla no
> less!  Let's not stop experimenting though, my guess is such a Dupla
> product will cost big buck$ !  Don't leave us hanging James, give
> us a link!

Dupla's English web site is at http://www.dupla.com/start_e.htm
Go to "New Products from Dupla". You will see a photo and some advertising
copy, but no real information. I have asked my contacts with Dupla UK for
some further information but they are as deeply in the dark as the rest of
us. For many German companies, it would seem that the rest of the world
either doesn't exist, or at least doesn't much matter.

In response to a statement of mine, Dwight responded:

> >It was also suggested that the real agent at work here is H2O2.

> That seems to make perfect sense to me.  H2O2 is light sensitive, that's
> why peroxide is mostly sold in opaque plastic.  If you follow the
> reasoning, then its not light that makes Barley straw work, but oxygen.
> Pure speculation here, but could pond straw in English ponds work b/c the
> oxygen is greatest AT THE SURFACE of the pond allowing the Rxn w/
> the straw
> & production of peroxides? Can it be that this fact is misinterpreted as
> the straw needing light to activate?

Well, it wouldn't be the first time that the true cause/effect of a piece of
equipment has been misrepresented/misunderstood/overhyped (check the
archives for discussions over substrate heating cables).

Thomas Barr makes the following comments:

> So I talked with a Dutch friend about this notion of H2O2/Straw further.
> He said it(H2O2) will definitely reduce algae if done properly.
> Reason is any change (typically raising) in REDOX potentials will
> do harm to
> the algae while the plants seem to actually like it. This makes of sense
> based on observations.

Well then, if that's the case, a small Ozone generator would raise the redox
potential of the water and the ozone, after it has worked it's magic on the
algae spores, would decompose into perfectly harmless oxygen.

David Aiken had written (from the archives):

> >Now, if someone brought out a reliable cheap redox test, I'd
> suggest that
> >we all go out and test the redox potential of our tanks and report

Therein lies the rub - redox is a measurement of electrical potential and
requires the use of an expensive and sensitive electronic meter. And like a
lot of things in life, the physical number you get from a test isn't nearly
as important as the direction of the slope of a series of measurements (i.e.
is the redox going up, down, remaining constant over time).

Thought experiments can be fun, but they are no substitute for hard data and
in an area such as this the variability involved in an aquarium makes both
comparisons and generalizations difficult, if not impossible.

James Purchase