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Re: Aquatic Plants Digest V3 #366

Hi Rich,

Don't I wish I had your soft water! (But the grass is always greener on
the other side of the fence.)

IF your alkalinity is 40 ppm -- and the LaMotte kit is good -- then your
water is only weakly buffered but, in my opinion, that is NOT your
problem! By the way, alkalinity of 40 ppm is equal to 2.2 "German
degrees", too little buffering on anybody's scale, and at pH 6.1 -- on
the bottom end of carbonate's ability to buffer at all.

May be that I am a little bit dense, but I do *not* see that you have a
problem with water chemistry:

1. For some reason you want to keep the pH at 6.1. Good. The pH stays
there, rock steady, but you are worried about that fact! Why? Most
people would be darn happy if their tanks stayed exactly where they want

2. Because you inject CO2, it must be a planted tank. Plants will use
CO2 and the tank's pH *HAS* to rise. It's not rising -- so CO2 is NOT
being consumed. Maybe the plants are not yet metabolizing sufficiently
(i.e. freshly planted) or for whatever reason. 

You might consider THAT a problem -- your plants are not growing -- but
that is a completely different problem, with a different solution, and
addition of sodium bicarbonate will NOT make them grow any faster!

So, I would think, that leaving the tank alone (but measuring the water
parameters) will result in eventual increased CO2 uptake by the plants
-- and then you will have to add CO2 to keep the pH at 6.1.

Relax, don't worry, don't add anything, enjoy your aquarium and let it
settle for about a month.


George S

(P.S. You don't mention whether you are fertilizing your plants & with
what. I know, that CO2 is called a plant "fertilizer", but I am thinking
along traditional lines -- nitrogen, potassium and phosphorus, as well
as trace elements. With such soft water, you probably have very little
trace elements present.)

> << On Sun, 5 Jul 1998, RDotta7777 wrote:
>  >
>  > When I hook up my CO2 system (using a pH meter to trigger the CO2
> injection),
>  > the water after a water change has a pH of approx 6.2.  I then allow the
> CO2
>  > to bubble in (at a slow rate).  In about 15 minutes my 125 gallon tank has
> a
>  > new pH of 6.1 and the system shuts off.  The pH never comes back up to re-
>  > trigger the CO2.  I have to add Sodium Bicarbonate to re-adjust the pH to
> kick
>  > the CO2 back on.  I have to do this every day.
> Roger replied:
>  This is rather odd behavior.  Not implausible, just odd.  So, instead of
>  answering the question I have to ask two more:
>  What is the buffering capacity of the water you're using?
>  Have you calibrated your pH device and/or checked its results with a
>  chemical indicator? >>
> It seems that the buffering capacity is the issue.  The water measures a
> Carbonate hardness of 40ppm with the LeMotte test kit which I equated to a dCH
> = 5.06.
> I just recently (two days ago) recalibrated the pH meter.
> I think that the water's buffering ability is low, but it seems difficult to
> stabilize.
> Thanks,
> Rich