[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: KH, pH, CO2 relationship

> From: Ryan Mills <millsman7 at yahoo_com>
> Subject: KH, PH, co2 relationship  
> 
> Paul, I think my co2 is a bit high and my ph a bit
> low.

	I'm pretty certain that your calculated CO2 number
(57 ppm), is wrong.  The problem with adding buffers other than
the CO2/HCO3- system is that it makes it impossible (with aquarium
kits) to measure the KH.  Your measured result will always be high,
so the calculated CO2 number will also be high.  These other buffering
systems also make it impossible to measure the CO2 concentration 
directly.  It's a lot simpler to stick to bicarbonate!  What is your
water like, straight from the tap?

> Suppose I want my ph to be about 6.5, the GH about 
> 4-5dh, and the co2 about 30.  That sounds good for the
> variety of life housed within.  My parameters are
> currently 6.2, GH 9dh (or 143 ppm), and co2 57.  I
> need a more accurate ph measuring method.  How about
> those Milwaukee or Pinpoint ph pens/monitors?  

	I don't think you need a more accurate pH measurement.

> If I can't get my desired ph and co2 by fiddling with
> acids and buffers or changing the KH, how can I?

	Start with the required KH, install a CO2 system, let things settle
down and measure the pH.  Get the CO2 concentration from the table.
If you don't like the CO2 result, fiddle with the CO2 system and let things
settle again, etc..  Don't use _any_ other buffering system.

>  How
> can I distribute co2 throughout the tank as evenly as
> before but just less of it?

	I don't think you will have a problem with uneven distribution
of CO2, because the times to reach equilibrium with the CO2 system and
the atmosphere are longer than the mixing times, if you have any sort
of pump/filter system in there.

  Is that the only way to
> modify the co2 level?  Flourish Excel is an organic
> carbon source used as an alternative to co2 (they
> say).  I mention it because I feel I don't have much
> control over the co2 with the yeast method.

	I have no idea if plants can actually _use_ this stuff. I 
gather that it is "polycycloglutaracetal".  If this really is an
intermediate that plants use in synthesis of carbohydrates from
CO2, I suppose there is no reason why it couldn't be used, if it
can get into the plant.  Plants would have no reason to have outer
surfaces permeable to this stuff though - usually they would have
everything to lose and nothing to gain.
	Glutaraldehyde is a dialdehyde - HCO(CH2)3CHO.  Acetals
are products of the reaction of alcohols with aldehydes.  These will
tend to be hydrolysed (come apart) in water, to release the aldehyde
and alcohols, both of which would probably be very popular with some
of the local bacteria.  The alcohols and aldehydes will be oxidised
quite readily to organic acids, which will also add to the KH measurement
confusion, though the amounts will almost certainly be too small to 
cause a significant problem.

>  As I
> mentioned in another post that tyes in with this one,
> I though about running an airstone for awhile at night
> as a possible control method.    

	In general, I don't think that this is necessary.  I've never
done it, and never seen any need.

> What if I get the GH down to where I want it but lose
> KH (which is happening as I do it)?  Calcium
> carbonate?  (but not enough to raise the GH too much
> as well)

	Sorry, I don't follow this.

> Some old polysperma leaves have tiny holes and a
> bolivianus sword is now showing clear patches on older
> leaves.  Potassium problem?

	Quite possibly.

> Flourish potassium is potassium sulfate.

	It's a _lot_ cheaper to buy it in a hydroponics or garden store.

> Equilbrium

	What _is_ this?


-- 
Paul Sears        Ottawa, Canada