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Re: CaCo (egg shells)

>From: Miles Morrissey <mmorriss at sophia_smith.edu>

>              Is calcium carbonate egg shells?  If I were to use a
>mortise and pestle to grind them into a powder would this work as a
>source of CaCo.  Secondly, adding a generic form of tums (which is what I
>use now) Th CaCo does cloud the water some but settles out in a matter of
>an hour or so.  I've been assuming that it settles onto and into the
>gravel where is slowly dissolves as well as settles into the gravel to be
>used by the roots after some time.  Is this accurate?

Yes, egg shells are mostly calcium carbonate.  I have ground them up with a
morter and pestle into a fine powder and dispersed them into an aquarium,
and, yes, they do dissolve slowly, but fast enough, by my observations, to
supply the plants and snails with the calcium they need.  Egg shells also
have organic matter in them.  I once tried heating them in a ceramic
crucible with a bunsen burner, and they turned dark, and then white, again,
as the organic matter became charcoal and then oxidized.  This heating also
drives off water and CO2, leaving calcium oxide.  When calcium oxide is put
in water it becomes calcium hydroxide, which is more soluble than calcium
carbonate, although still not very soluble.  Carbon dioxide in the water
reacts with the calcium hydroxide to produce calcium carbonate, some of
which can react with more CO2 to become calcium bicarbonate, which is quite
soluble.  In summary, the solubility of calcium carbonate is quite low, and
the solubility of calcium hydroxide is a little less low.  If you want to
add calcium hydroxide, you can add small amounts of lime without worrying
that it will make your tank highly alkaline.  By small amounts, I mean
around 1/4 teaspoon in a fifteen gallon tank.

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174
In Jackson, Mississippi with sunny, pleasant spring weather.