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Re: Aquatic Plants Digest V4 #935

Damian Barton wrote:

> Hello Well there's something I've been wondering about. I'm pretty sure most
> people will be amused but here's my question anyway: What's in the air?

Dry air is mostly inert nitrogen gas with smaller quantities of other
gases.  In descending order they most imprtant other gases are oxygen,
argon and carbon dioxide.  Air also contains a few percent water vapor.

> More
> specifically if I used an air pump to pump air bubbles into a Co2 reactor what
> gases would be dissolved?

You would get (by my calculations) about 15 mg/l nitrogen, 8 mg/l
oxygen, 1.2 mg/l argon and 0.4 mg/l of carbon dioxide.

> Why if there's enough Co2 in the air for terrestial
> plants would there not be enough for aquatic plants from air pump bubbles
> dissolved in a reactor in an aquarium?

Air bubbles won't dissolve very well. 

Air and well-aerated water contain about the same amount of CO2 on a
weight/volume basis (I calculate about 0.46 mg CO2 per liter of water,
and 0.59 mg CO2 per liter of air), but in water there's a problem
getting the CO2 to the plants.  Photosynthesizing plants can use up all
of the CO2 in the water adjacent to their leaves.  After that, any
additional CO2 they can get has to come through the already-depleted
layer of water next to the leaf, and that happens slowly.  If CO2 levels
are low (as with aerated water) the barrier is a bigger problem then if
the CO2 levels are high.  The barrier is a much smaller problem in air.

> Maybe someone out there can stop laughing for a second and explain why it won't
> work :-)

Actually, if the CO2 level in your tank is lower than the CO2 level in
aerated water then aeration might help a little.  Aeration is a futile
effort unless you also maintain a strong current to keep the water

Roger Miller