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Re: [APD] CO2 and Algae

Thomas Love wrote, in part:

> Therefore, for the maxim "add more CO2" to be the best advice >for an
>sufferer, I think these together are necessary and sufficient >conditions:

>1. A well-planted tank;
>2. The plants having good root systems.
>3. With a fertile substrate.
>4. Good lighting.

>I suspect most people with algae will likely be failing on all >four
>so adding CO2 will not help them.

>CO2's effect on the pH and phosphorous adsorption may assist >but is
>to be sufficient alone.

I beg to differ from the above.  The largest single material in plants, by
dry weight, is carbon.  Carbon is not from the substrate, but for aquatic
plants from dissolved CO2 in the water.  Depending on the definition of item
#4 on the list given above, that list could be a prescription for algae
regardless of the mineral content of the substrate if there is insufficient
bio-available carbon in the water.  The next two materials, hydrogen and
oxygen are rarely to never in short supply, but also not from the substrate.
Only from the forth material down on the necessary material list are the
materials commonly from soil or substrate, and most or all can be absorbed
directly or secondarily from the water - if added as liquids, some may come
out of solution and then be root-available.   But without sufficient carbon
being available, the limiting factor for aquatic plants will be the carbon,
and growth will slow or stop. Then algae will have the advantage.  The
benefit of supplemented CO2 is that carbon will not be the limiting factor,
not by pH or other effect of CO2 supplement.

Certainly it is possible to operate planted tanks without supplemented CO2 -
I do it all the time - but some of my tanks must have added bio-available
carbon by other means if I want to avoid algae issues.  The lighting on
those is just a bit too "good" regardless of the substrate or other liquid
mineral supplements.

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