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Re: [APD] Allelopathy was Re: pearling after water changes Vol 2

On 1/29/07, Jerry Baker <jerry at bakerweb_biz> wrote:
> Liz Wilhite wrote:
> > Yeah, it is but it's role in aquaria is hotly debated. Walstad cites a
> > number of papers in her book and attributes the lack of algae in her
> tanks
> > to allelopathy -- she recommends no water changes.  Tom has posted a
> number
> > of references -- quite a long number of them -- to this list that
> contradict
> > the references Walstad cites. There is an article about allelopathy in
> > planted aquaria on the Tropica website, written by Ole Pedersen if I
> recall
> > correctly, that supports the idea that allelopathy has a limited role at
> > best in aquaria.  I think that is Tom's conclusion as well.
> It stands to reason that if plants can release enough allelopathic
> chemicals to affect other plants in virtually unlimited volumes of water
> that those chemicals would have even greater effect in the confines of
> the aquarium. Of course, that conclusions assumes some things not least
> of which is that the aquarium environment doesn't cause plants to reduce
> or halt their release of allelopathic chemicals.
> > My personal belief -- and that is all it is at this point -- is that Tom
> is
> > correct about exposure to CO2 gas making a big difference in growth but
> I
> > haven't seen anything yet that really indicates that is true with one
> > exception.  I've noticed that when the first bit of panted, submerged
> water
> > sprite reaches the top of the tank that the growth of the entire plant
> is
> > much, much faster than when the entire plant is submerged.  I see that
> in
> > water sprite growing in both CO2 and Excel tanks.  I also observed a
> change
> > in growth rate when I rescaped the CO2 inject tank and moved the water
> > sprite from a place where CO2 bubbles were blown onto the plant to the
> one
> > spot in the tank that has no bubbles.
>  Aside from the bubbles, could there
> have been a CO2 concentration difference that would explain the observed
> effects?

You bet there could be a concentration difference!  That is one reason I
don't consider this anything approximating proof, merely suggestive.  There
are lots of things that could be going on.  But it is true that many people
have reported that exposing aquatic plants to  CO2 bubbles seems to yield
increased growth, some of them long before anyone was talking about mist.  I
remain a bit skeptical but there is substantial evidence to warrant a closer

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