re: CO2, qeustions

---------- Forwarded message ----------
From: psears at emr1_NRCan.gc.ca (Paul Sears)
Message-Id: <9701241633.AA15177@emr1.emr.ca>
Subject: Re: CO2 , questions
To: Aquatic-Plants at ActWin_com
Date: Fri, 24 Jan 1997 11:33:51 -0500 (EST)

> From: STDIXON <stdixon at bechtel_com>
> Subject: CO2 Reactor Efficiency
> I have a Sandpoint CO2 setup for my 125 gal planted tank.  Starting with
> RO/DI water, I use a carbonate buffer (Kent PH Stable) to obtain 2-3 dKH. 

	Sodium bicarbonate would be cheaper.  Calcium carbonate (powdered,
which dissolves to form the bicarbonate) would be good, too.

> > The pH dropped nicely from 7.2 to 6.8 (Pinpoint pH monitor) with some daily > fluctuation of .3 or so.  With 2.5 dKH and a pH of 6.8, the CO2 level MUST
> be about 12 mg/l, unless some of the stuff I'm adding to the water is
> resulting in bad KH readings.  Right?

	The KH readings should be O.K., provided the seachem stuff _is_
just a (bi)carbonate buffer.
> My question is:  Should I be thinking about a more efficient reactor? 

	How well are the plants growing?  You may have enough already.
It may also be that your current method will empty the tank too quickly
for your liking, but CO2 is cheap, and commercial reactors are not!

> From: Onis Cogburn <k5vkq at ix_netcom.com>
> Subject: questions and info.
> >
> >1) Potassium sulfate, muriate of potash and potassium carbonate: 
> I have been using
> muriate of potash but as this is half KCl,

	It is _all_ KCl.  The nonsense on the package about "K2O content"
tells you how much K2O there would be if the K were actually present
as K2O, which it isn't.  "Muriate of potash" is a name that is at least
a hundred years out of date.

> I am worried about long term
> accumulation of KCl.

	You _want_ the K there, and the Cl isn't likely to do a lot
of damage at the concentrations you will get if you do some water

>  I began to wonder about the possibility of
> substituting potassium carbonate instead.  

	This is O.K., but will produce a very alkaline solution, and
will tend to increase your KH a little (you don't add much).  The
trace element mix might not like the solution's pH.  The magnesium
would also precipitate out of the combined mix as MgCO3.

> Can I use potassium carbonate instead of potassium
> sulfate and if so how much?

	About 90% by weight, compared to the K2SO4, provided the carbonate
is anhydrous.

> >
> >2) Tetra and SeaChem nitrate test kits:
> >I have been using a Tetra nitrate test kit for monitoring my nitrate levels
> until last week.  I ordered a SeaChem nitrate/nitrite test kit because of
> the low resolution of the Tetra kit.  Herein lies the problem.  When I
> measure the nitrate with the Tetra kit, it is 10 to 12.5 ppm.  The SeaChem
> kit reads .2 ppm!  What is my problem?  

	Are they both giving NO2-/NO3- concentrations, or is one giving 
the concentrations expressed as the N in the NO2- or NO3-?  For nitrate,
the difference is a factor of 4.4.  Your difference is larger than that,
but it may account for part of the problem.

Paul Sears        Ottawa, Canada

Finger ap626 at freenet_carleton.ca for PGP public key.