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Re: [APD] Re: The why of the Barr method

We won't know unless someone actualls measures the chems
suspected of being there. Until then, a nod is as good as

--- Jim Seidman <js5 at seidman_net> wrote:
> Daniel Larsson quotes Dr. Ole Pedersen in saying:
> "Can allelopathy be used to control algae growth in the
> aquarium? The
> answer would be NO!"
> I've read Dr. Pedersen's article before, and it doesn't
> make sense to me.
> He says in the same paragraph:
> "It is much more likely that this general observation is
> due to efficient
> competition for resources (light, nitrogen, phosphorus
> and CO2) from the
> higher aquarium plants and this may prevent the algae
> from ever getting a
> hold in the tank."
> If this explanation was correct many people would have
> tanks overrun with
> algae. Algae need very little light. Many people keep
> their tanks amply
> supplied with NO3, PO4, and CO2 all the time.
> I neglected one of my tanks for a few weeks and let NO3
> levels get to about
> 0.2 ppm. I'm only now recovering from the algae takeover
> and green water
> that ensued. How I am fixing it? By dosing KNO3 and
> NaH2PO4. And it's
> working great! If nutrient competition was the answer my
> fertilization
> would make it worse, not better.
> To Dr. Pedersen's suggestion of controlling algae by low
> fish count (i.e.
> limited nutrients) and frequent water changes: I tried
> it, it didn't work.
> I have never heard of it working for anyone else either.
> I also notice that Dr. Pedersen mentions in the same
> article that there are
> plants that pump out quite large amounts of allelopathic
> toxins "under
> natural circumstances." My theory is that this effect
> ratchets up an order
> of magnitude under high-nutrient conditions.
> Again, allelopathy explains the observed fact that
> high-nutrient aquaria
> are often algae free. Dr. Pedersen's theory of nutrient
> competition
> wouldn't predict that result.
> - Jim Seidman
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S. Hieber

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