Re: CO2 Question

["David A. Youngker" <nestor10 at mindspring_com>]

> Date: Mon, 6 Jan 2003 16:28:06 +0000
> From: Kevin Buckley
>
> I was recently reading a booklet from a German
> manufacturer of aquarium CO2 products & it made a
> number of statements that, taken together & to their
> logical conclusion, would imply: IF ALL OTHER
> FACTORS ARE EQUAL, CO2 would diffuse out of a
> body of water faster if the KH is lower (given the same
> starting concentration of CO2 in solution).

Then again, it could be a matter of *perception*. In cases like this, it
would be _very_ beneficial if you would provide some indication of what
these statements say _as written_.

> So, in aquarium terms, it would be better (i.e. less CO2
> loss) to have a higher KH & maintain a higher pH, than
> to have a lower KH & maintain a lower pH, to achieve
> whatever target CO2 level you require.

See what I mean here? This statement in and of itself, within reasonable
limits, demonstrates a situation more beneficial to the plants as it
provides a greater availablility of inorganic nutrients to go along with the
carbon. But it doesn't arise from the latency of the CO2 - merely the higher
concentration of inorganics.

> Does anyone know if this has any basis in fact?

The "latency" I mentioned in the previous paragraph is the term used to
describe the "linger time" of the CO2 within the water column. How _much_
CO2 dissolves within the water is dependent on partial pressure and
temperature, and is constrained only by its solubility limit. It _doesn't_
depend on what else in in the water, like other gaseous or solid solutes.
Nor does the presence of these dictate how _long_ it will stay in the water.

The things that *do* control latency? Dissolution, diffusion, plant
absorption, turnover rates and surface movement are certainly on the list,
and it's not a _complete_ list, but KH isn't on it...


-Y-

David A. Youngker
nestor10 at mindspring_com