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Re: Aquatic Plants Digest V6 #252

> Date: Mon, 11 Aug 2003 19:14:02 EDT
> From: Billionzz at aol_com
> Subject: CO2 / pH change,how long?
> Hi,
>  I have got my 120g tank up and running with pressurized CO2.
>  How long does it take to see an effect on the pH? I started
> with 1 bubble 
> per minute yesterday and the pH went from 8.2 to 8.0, so today
> I changed it to 3 
> bubbles per minute.

Noted your change to 3b/sec
3b/sec should be enough to adjust the CO2 levels to where you
want them(20-30ppm) in this volume of water. You might need a
bit more, not much. Other wise I'd look at mixing/CO2 reactor
methods/splashing/water surface turbulance etc for CO2 losses.
>  I also have a GH of 13 and a KH of 10, does this mean that I
> will be using 
> extra CO2 to get the same pH as someone with lower GH/KH
> levels?

Yes, the _same_ pH. But you will have more CO2 in your water
than the lower KH water at the same pH. See below the exmaple of
KH of 4 vs KH of 10.

GH is not part of this table for achieving a good CO2 level for
you. 3 degrees or about 50ppm and above is good. 
You don't need to worry about GH in your case.

Hard,medium soft KH's etc, doesn't matter, CO2 is what the
plants want, see what the KH is, then add enough CO2 to get that
pH according to the table: 

A KH of 10 means you need to shoot for a pH of 7.0-7.1 for good
CO2 levels during the _entire_ lighting period. 

At a KH of 4, your target pH will be pH 6.6-6.7 and this is the
_same_ CO2 level as the KH of 10 and pH 7.0-7.1 plant tank.
That's all you have to do. Soft/hard etc, don't worry about it,
it's not going to help you grow plants better with soft water.
Plants in hard water or soft will use/take up the same amount of
CO2 from the water. Likewise more acidic water also will not
help improve plant growth by itself(say a KH of 4/pH of 6.6 etc
vs your tap water), it's all about the CO2.

You will add the same amount of CO2 gas to both tanks with the
different KH's since you are trying to get the same CO2 levels
in both tanks.The uptake of CO2 by the plants, all things being
equal except for the KH's/pH's should be the same/very similar
in both exmaples I mention here. 

Tom Barr


> Thanks,
> Bill

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