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CO2 Concentration


  1. DIY-CO2 and "Tetra Bells"
    by ("Niels M. Sampath") (Tue, 1 Feb 1994)
  2. CO2 in nature
    by ac554-at-FreeNet.Carleton.CA (David Whittaker) (Fri, 3 Mar 1995)

DIY-CO2 and "Tetra Bells"

by ("Niels M. Sampath")
Date: Tue, 1 Feb 1994

In article <2800573-at-hplvec.LVLD.HP.COM> booth-at-hplvec.LVLD.HP.COM writes:

>In our manual CO2 setup, the CO2 runs all the time, day and night.  The
>pH varies from a minimum of 6.8 (early morning) to 7.1 (maximum 
>photosynthesis).  This correslates to a CO2 range of 22 pmm to 11 ppm. 
>I would consider 30 ppm to be the beginning of the "dangerous" region. 
Might find this interesting: (from `Nature and Aquarium', a book by Berti 
Gesting [plant guru of `Practical Fishkeeping Magazine' and owner of 
BioPlast UK)])

      `We know today that a sufficient CO2 supply is essential for a 
      natural and healthy biotope  - but what is a sufficient quantity of 
      CO2? The occasional suggestion that CO2 levels of more than 20 mg/L 
      could be dangerous to fish (a statement possibly adopted from trout 
      farming) is completely wrong as far as our aquarium with tropical fish 
      and plants is concerned. Neon tetras, Angels, and Discus, for instance,
      show absolutely no signs of discomfort even at 100 mg of CO2 per litre.
      Black Mollies still feel very comfortable at 500mg/L, and Guppies breed 
      happily at 800 mg/L. (This incidentally, proves also that the "old 
      wive's tale" about Black Mollies being brackish fish and needing a 
      spoonful of salt in the water should have gone out together with 
      burning witches at the stake).

      It is, of course, important that such exteremly high levels of CO2 are 
      introduced gradually over 2-3 days to make it easier for the fish to 
      adapt. The recommended CO2 contents, natural and sufficient for all
      plants and at the same time completely safe for all fish should be 
      35-45 mg/litre.'

And from the Dennerle book `System for a Problem-Free Aquarium':

        `We recommend a CO2 level of 35-40 mg/litre'.

Personally I think CO2 levels have to be distinguished from O2. I think
the jury is still out. Perhaps one day   along with pH and hardness values,
fish atlases will list species O2 and CO2 `natural' levels as well?

Niels M. Sampath      Internet:



CO2 in nature

by ac554-at-FreeNet.Carleton.CA (David Whittaker)
Date: Fri, 3 Mar 1995
Newsgroup: rec.aquaria

In a previous posting, Roberto Khey Solis ( writes:
> after reading all the CO2 articles in the ftp sites and following a few 
> articles in the newsgroups, a thought struck me. 
> in the aquarium, concentrations of CO2 range about 1-2 ppm which 
> apparently isn't really enough for fast growth of plants.
> with injected CO2 you can get your levels in the 10-20 ppm range. at 
> these levels plants grow pretty rapidly.
> what are the CO2 levels in nature? i want to say that they are the same 
> as in the uninjected aquarium--after all, you don't see CO2 tanks lying 
> in the rivers and lakes (not usually, anyway :) )
> is plant growth in the wild mainly driven by the fertilers (trace 
> elements, etc.) ?

Good question. From what I have read, the sediments in which
aquatic plants grow contain a huge amount of carbon (up to 100
times the level found in the surrounding waters). I believe that
they store this as malic? acid.

Many of plants are amphibious and obtain their carbon dioxide from the

As well some such as hygro produce a thin layer of H+ ions
at the leaf surface, and are thus able to make use of bicarbonates
in the water.

In The Optimum Aquarium, Horst and Kipper found relatively high
(8-14 mg/l) of CO2 in a S.E. Asian stream. This they attributed
to spring/ground water that was leeching into the stream and which
was determined to have very high levels of many nutrients including
iron and CO2.

If you tested the lake water in front of your cottage, I bet that
you would get 0-4 ppm as CO2 and most of that would be the result
of limestone and acid rain. Just guessing.

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