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Re: Aquatic Plants Digest V4 #930

Hello Armand,

> Date: Thu, 29 Mar 2001 16:42:53 +0200
> From: "Chin Kwie Joe AJST (Armand)" <ajstchinkwiejoe at hr_nl>
> Subject: RE: Aquatic Plants Digest V4 #929
> #> Date: Wed, 28 Mar 2001 08:50:31 -0600
> #> From: "Stuart" <stuart at nbtx_com>
> #> Subject: Re: CO2 controller....
> #>
> #> Dave Gomberg Wrote:
> #> >I really don't understand what all this is about.   There
> #are huge pH
> #> >swings in natural ponds, and yet the fish and plants do
> #fine.   What is
> #it
> #> >we are trying to achieve here?
> #>
> #>
> #> The idea is to adjust KH to about 4.5 - 5 and then use CO2
> #to lower the PH
> #
> #sorry, this idea is *NOT* correct. You purge CO2 _only_ to get
> #(or hold) a
> #certain level of CO2, let's say 15 mg/l CO2. If the pH will
> #decrease by this
> #purching and you don't like this, then you have to increase the KH. CO2
> #should _not_ used for changing the pH!!! Again: CO2 is a
> #fertilizer for the
> #plants and not a tool for changing the pH.
> #
> #Regards Klaus.
> #
> This is my first repay and i hope it comes in correct.
> Klaus,
> Maintaining the correct amount of CO2 is a function Ph versus KH.
> So for an aquarium with a KH of x the correct Ph would be Y.
> Ergo: a Ph controller can achive this by increasing the amount of CO2 and
> thereby lewering your Ph.

your mathematical logic is correct, but not the biologic logic ;-)
In a planted tank it is necessary, to have a certain level of CO2 as
fertilizer for the plants. If you don't regard this, plants try to cover
their need by the KH of tank water with consequences of pH. So, if you purge
CO2 by a bottle, make sure, that a concentration about 15mg/l CO2 is
available. If you have const. KH, a good working highpressure regulator at
your bottle and const. lighting, the pH will also be constant (forget in
this moment the swing between morning and evening). In this case is no need
for a pH controller. Next case: pH controller is installed, CO2 level is
const. and s.valve is closed. Caused by a failure, whatever, ph increasing
is monitored (KH is still const.). As consequence, the controller opens the
s. valve and purge CO2 into the tank. In case of a hardware failure in the
controller unit, you will get to lat or never the set point of controller
and CO2 is running and running, you overdose CO2 and your fish get poisoned.
Do you understand, what I will express? If you habe a pH controller and you
will install it, then use it _not_ as a controller but as a "low level pH
shut down switch". That means, use _only_ the switch off function of the
controller. Example: Your KH might be 6, your desired CO2 = 15mg/l. As
result you get a pH of about 7.1 My recommendation is a highest CO2
concentration of about 30mg/l, that means a pH of 6.8. Adjust the setpoint
of the controller to 6.8 pH with the function to close the s. valve of CO2
supply. Now you are at the safe side and the fish will thank you!
BTW, there is no need to keep the pH in the tank const.!

> In my case i have a KH of 8, and Gh of 14 and a Ph of 8 without CO2.

this means a CO2 of about 2,5mg/l, absolutely to low!

> With
> this KH the correct amount of CO2 will beachived at an Ph of 7. So
> Ph to 7 by CO2 injection has the desired effect.

this means 26mg/l CO2, ok., but don't get higher.

> Are am i missing something?

I don't know ;-)

Regards, Klaus.
> Regards, Armand