Re: Calcium and buffers

> From: Dirk 
> Date: Mon, 10 Feb 1997 11:55:09 -0600
> Just a thought, but wouldn't calcium carbonate be a better buffer for
> a planted tank than sodium bicarbonate, since sodium isn't all that
> desirable, and someone noted recently that some plants (especially
> Echinodorus sp, right?) are often calcium deficient?

The simple answer is ... "It depends."

If you want a "soft water" environment, a discus tank for example, you
may not want much general or calcium hardness.  In this case, calcium
carbonate by itself would not be appropriate due to the calcium you
would add and sodium bicarb would be the hot setup, sodium be damned.
If you want a "hard water" environment, calcium carbonate plus some
magnesium sulfate is perfect.
Also, if you are anal retentive like me and want a certain KH and GH,
then a specific mixture of the two is appropriate. 

> Boy oh boy am I having a rough time getting my water properly
> buffered.  I am having to dose about every other day with some source
> of KH to keep up with my yeast CO2 (producing a little more than 1
> bubble per second).  I'm thinking of putting a piece of shell in the
> tank.  Thoughts?

In my experience, KH (carbonate) is not used up at a very rapid rate.
In our tanks, we don't see KH change (given the resolution of the
Tetra KH test kit) between biweekly water changes.  Are you adding
sodium bicarb?  What KH level are you shooting for?  Do you have peat
in the tank?  Are you titrating with nitric acid (i.e., do you have an
enormous fish load)?  Something is not "right", here.
The buffering mechanisms of sodium biocarbonate and calcium carbonate
are the same.  Adding a shell (just calcium carbonate in an attractive
shape) only slightly increases the amount of buffering you are adding
(because you are then adding slightly more carbonate, not that a shell
is anything special).  Also, shells dissolve *really* slowly, so you
probably would not notice any effect.  Find out where the buffering is
going first.