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Re: Biogenic decalcification

To: Aquatic-Plants at actwin_com
Subject: Re: Biogenic decalcification
From: Paul Sears <psears at nrn1_NRCan.gc.ca>
Date: Sun, 11 Mar 2001 15:27:26 -0500 (EST)
In-Reply-To: <200103110848.DAA14791 at actwin_com> from "Aquatic Plants Digest" at Mar 11, 2001 03:48:04 AM

> From: "L. Merrell" <merrell at u_washington.edu>
> Subject: biogenic decalcification?
> 
> Hi. I posted a few days ago regarding my red melon sword with distorted
> leaves. I measured my various water parameters today and found that my dKH
> had dropped from a usual level of 4-5 down to 1 dKH. Could this be a case
> of biogenic decalcification? My other plants include: cypts, duck weed,
> azolla, glosso, rotala indica, bacopa carolinia, a red lotus and various
> swords.  Should I simply to a water change and watch the KH closely or do
> I need to dose with a carbonate source? Sodium bicarb or calcium
> carbonate?

	Biogenic decalcification is the removal by the plant of CO2 from
a solution of _calcium_ bicarbonate.  Calcium carbonate is precipitated,
and should be visible.  You didn't say what your GH is, but from the
calculations I have done on the chemical equilibria involved, I very
much doubt that you will get this with water that isn't pretty hard
(say GH10, KH10).  The pH will go very high, too - well over 8, probably
near 9.  It cannot occur with sodium bicarbonate.


-- 
Paul Sears        Ottawa, Canada

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