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Re: Not Co2 again!

> Date: Mon, 30 Dec 2002 19:06:03 -0500
> From: "Sharon Stewart" <sharon at stewartcentral_com>
> Well, I find myself in need of setting up my Co2 system on my 38 gallon
> tank. I'm having wicked pH problems, <sigh>. The parameters are:
> 38 gallons
> 55 watts compact fluorescent
> tap KH 2, sometimes 3
> tap GH 6 now, usually 8 or more in the Spring-Summer
> tap pH 7
> tank KH-2 for a day or so after water change, not measurable after that
> tank GH-6
> tank pH, see below
> I change the water weekly. By the end of the week I have no KH that I
> can measure, and the pH swings up during the day, and down at night.

I would guess that you have very little KH (in terms of "carbonate hardness"
or concentration of CO3). A KH test kit is actually measuring total
alkalinity, of which carbonate hardness is only one part. For example,
phosphate in the water will add alkalinity. In my experience, carbonate
hardness (CO3) is "used up" very slowly, if at all, so what you are seeing
change is not really KH.

> And should I be adding some baking soda to up my KH? And, if I should
> add baking soda, how long will the effect last? In other words, how
> often do you have to add it?

Yes, add enough baking soda to give you 3-5 degrees (50-100 ppm) of
alkalinity. Add a little, measure, add more if needed. That should last
until you do the next water change, when you need to add enough baking soda
to compensate for the lack of KH in the fresh water you are adding.

> I've read everything I could get my hands on and my head is swimming, so
> any advice is appreciated. I'm guessing that I'm seeing biogenic
> decalcification, but that is only a guess.

No, it's probably not that.

George Booth in Ft. Collins, CO (gbooth at frii dot com)
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