RE: Determining CO2 Concentrations in Natural Waters

[David Sanchez <barbax2@yahoo.com>]

Man oh man did we ever get off topic. Ok well this has
gotten long and quite boring but here goes.


¡§> I'm afraid that it is you that has confused a few
> issues. Let's see if we
> can walk through this in an academic manner and
> arrive at some sort of
?« "consensus", shall we?¡¨

Indeed we shall however you used allot of words David
yet you failed to really say anything relevant to the
topic here. Perhaps I shall explain this relationship
in ¡§plain ¡§ English so the rest of the group can
understand. I think for the purposes of this audience
we should proceed in a more practical matter. Please
explain how this affects our aquariums and fish
keeping and the"Topic" how we do or do not need CO2 in
our aquariums. 

The pH of  a natural body of water is in large part
determined by the chemistry of carbon dioxide. Dawes,
C..J. 1981 Aquatic Botony.

CO2 is a very soluble gas which is normally found at
concentrations of 45-55 ml/l in natural bodies of
water far less the is found in the air we breath. CO2
enters the water system via land run off, through the
surface from the atmosphere and is released by aquatic
plants and animals during respiration. In addition the
action of bacteria breaking down waste products will
also release free CO2 as they metabolize fecal matter
and dead tissue.

¡§the CO2
> concentration as essentially
?« fixed¡¨

That is very wrong and your mistaken David Y. I don¡¦t
know about your tanks but there is feces and loads of
bio activity that will release CO2 in to my system not
to mention fish respiration. This goes to my argument
about water changes as we allow the water to
accumulate DOC¡¦s, nitrates and other inorganic
compounds the pH will go down.

Let me explain this further. Most of the CO2 combines
with water (remember hydration from Bio 101) and forms
a weak acid-carbonic acid. Less the 1% of the CO2
present in a body of water is in the form of ambient
CO2. The carbonic acid then dissociates into carbonate
bicarbonate ions. These compounds are in equilibrium
with each other. That is to say that the chemical
reactions shift back and forth with the changing
conditions and retain the same ratio or chemical
balance.  This is the pH equation I was talking about
David Y.

¡§There is no "pH equation", per se - only the
> _definition_ of pH, which is an
> inverse log of the actual *count* of hydrogen ions
> in a solution. It's a log
> scale because we're dealing with _huge_ numbers
> here, and the numbers we
?« _do_ use are in effect the *exponent* of the
value¡¨

¡§Did you catch that "fixed" part? That means it
> doesn't change. Therefore,
> the only thing really influencing the final pH is
> the bicarbonate
> concentration.¡¨


¡§The rapid increase or decrease of CO2 has the
greatest immediate effect on the pH of a natural body
of water. Removal of CO2 lowers the amount of carbonic
acid and pH increases. Addition of  CO2 increases the
amount of carbonic acid and pH decreases¡¨ Bardach,
J.E., J.H. Ryther and W.O. McLarney. Aquaculture

This is why we don¡¦t need a CO2 injection system if
we have enough free CO2 in our system through a low KH
and low pH there will be plenty of carbonic acid
present , this we get from the chart. Not to mention
the metabolic functions of fish and waste decay.

¡§It is _not_ the incorrect way of looking at this -
> it _is_ the *only* way to
> look at this. The "KH" is THE primary natural buffer
> within the equation. So
> if you have no buffering agent, you can have no
?« > buffering. ¡§

I don¡¦t know where you are going with this but I will
stick to what I have said. It seems you have used
allot of big words david but you have failed to
explain anything  in any practical sense. I don¡¦t
really care about chemistry other then how it relates
to my fish keeping and breeding. Here is the bottom
line in plain English no fancy words needed.

A low KH will help keep a low pH. A high KH will have
a tendency to a high pH. If you are having trouble
maintaing a low pH say, 5.5 or even 4.5 then you will
need a KH of 0 to get there. Simple no fancy words
needed and everyone understood.

¡§There _are_ other
> buffers at work in our Apisto tanks down at the
> ranges we work on, and their
> related to the humics most of us introduce through
?« peat/tannin filtering¡¨

Thanks for confirming what I just said.

¡§But be forewarned - my reading includes people like
> Arrhenius, Bronsted,
> Lewis, Dalton, Henry, LeChatlier, Boyle, Charles and
> their ilk. And my
> practical experience is approaching the fourth
?« decade...¡¨

Ok? I don¡¦t know what to think of that¡K.. Anyway I
can appreciate your knowledge of Chemistry David Y.
Obviously you have a love for this stuff. However you
have failed in my opinion to explain anything only say
allot of big words about pH. For the purpose of this
forum I would suggest you take it slower and put the
knowledge into practical terms. I don¡¦t really care
to hear about pH mombo jumbo I want to know how it
effects my tanks and my breeding. I also think you
need to explain things in terms that would be more
relevant to this audience. I am far from an expert on
Chemistry. But be forewarned ?º I do know what works
in the aquarium and why from my 2 decades of
experience of putting them into practice.



You're a Floridian - ever go looking for Elosoma
(dwarf sunfish)?
Particularly Elosoma evergladei? They frequent soft,
acidic springs 
with
little DOCs and an excellent source of carbon - the
gas that bubbles up 
in
the spring. Check out the types of plants that grow in
those 
headwaters.

Actually your very incorrect these fish are found in
water with a pH of 7.8-8.2 and a KH of 15 and 21 DH,
in Florida anyway. And I have not seen any of the
things you talk about. Ellassoma sp.  that I have
found have always been in hard alkaline water. If you
understood Florida you would know why an acidic soft
water spring is impossible. We have the aquifer. It is
liquid rock. Perhaps the CO2 bubbling is correct but
do lakes have that? Ponds? Other rivers?  BIG NO! Also
since the water is from the aquifer, no aeration kinda
like a well, hint, hint you guessed it lots of CO2.

And now that we are finally back on track to the topic
of discussion. Since you are so versed in water
Chemistry perhaps you could explain why CO2 is needed
in an aquarium? I will stick to my argument regarding
free CO2 in a system of water. You have said many
words David Y yet you have not explained this. Which
is after all our topic of discussion. A CO2 injection
system is not needed when there is already enough CO2
in an aquarium with LOW KH and pH. If you disagree
please explain why you do so. Hopefully in a manner
that we can all understand and relate to. Mind you I
fully understand all you have said though I find such
information rather mundane. Perhaps you could show a
deep understanding of your knowledge through applying
it to our topic of discussion mainly why we do or do
not need a CO2 injection in an aquarium. Keep well. I
hope you get better from your cold.

David Sanchez







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