Off-topic water chemistry post

Well, this post is off-topic, I suppose, but since the digest could
sometimes be more accurately titled the "Water Chemistry Digest", I
figured I'd give it a go.  Scream at me privately if you feel like it.

My question may be based on my imperfect understanding of solubility.
I'm trying to miz water for Malawi cichlids (with some Java fern,
Hygro, Java moss, and horwort -- we're on topic now!).  The breakdown
of prevalent ions in the lake is like so:  	

	Cations:  73% Ca++, 27% Mg++
	Anions:  88% CO3--, 12% SiO3--

GH is 6-10 DH.

A source for silicate is beyond me, but I was planning on using
powdered limestone (via the garden shop) to get my Ca, Mg, and CO3.
This is CaCO3, and MgCO3, primarily the former.  Thing is, I found
that the solubility of CaCO3 (I don't know what it is, just that it's
low) is too low to achieve the required hardness.  How else would I
make the water without introducing additional ions?


Brian T. Forsythe
crom at cris_com

Every picture is not worth a thousand words; besides, I think I'd rather have the thousand words.