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Re: Calcium issues


This is a useful and well timed conversation for me, as I suspect I'm in the
same boat calcium-wise as Tom Brennan, with my super-soft NW water.  OK, I
get saturation point.  My question is this: How do I figure out how much in
the way of marble chips or oyster shell or whatever do I stick in the sump
of my 100 gallon to raise my calcium level a bit, but not bump the hardness
over about 4 or 5 degrees (Sorry about using degrees rather than ppm, but I
use a Sera test kit, so degrees are easier for me to think in).  The problem
I have is that I'm in the final stages of finishing my Bachelor's degree, so
I'm running around like a crazy person and don't have a lot of time to do
water tests, sleep, eat, breathe, etc.  I also use CO2 injection with a
Sandpoint controller, so my pH will stay at 6.8 until my water reaches
stupid-hard levels, unless I put time into paying attention to measuring it.
I'd really like to be able to put some chips in the tanks and forget about
them; is this a possibility?

Justin Collins, in Bellingham WA, where its finally sunny!
> Date: Thu, 03 Jun 1999 10:51:33 +0000
> From: George Slusarczuk <yurko at warwick_net>
> Subject: Re: Aquatic Plants Digest V3 #1068
> Hello Tom,
> You just had to pick a question that does NOT have a clear cut answer!
> :-))
> The *saturation* point is when no more of a substance dissolves, or
> rather when the substance in solution is in an equilibrium with the
> solid phase, out of solution.
> The *solubility* of calcium carbonate [CaCO3] in *pure* water is only
> about 17 ppm (i.e. about 1 "German degree"). It is a well known fact,
> that calcium BIcarbonate [Ca(HCO3)2] is much more soluble in water than
> calcium carbonate. Calcium bicarbonate is unstable, exists only in
> solution, one can not isolate it & put in a bottle. The way one prepares
> it, is to add CO2 to the water which is in contact with excess solid
> CaCO3. The CO2 (actually carbonic acid, H2CO3) reacts with the calcium
> carbonate in solution, forming the bicarbonate, and shifts the
> equilibrium, allowing more solid calcium carbonate to dissolve... and so
> on.
> If enough CO2 is present, a lot of CaCO3 can dissolve. My well water has
> 430 ppm CaCO3 hardness. I have heard of places with REALLY hard water
> ("liquid rock") with over 1,000 ppm CaCO3. So, depending upon available
> CO2, the calcium concentration will vary.
> Most solid-liquid reactions are slow. In an aquarium with fish one does
> not want to change the water parameters rapidly -- it puts stress on
> fish, might even kill them. So, a slow coming to equilibrium, in my
> book, is an advantage: Just place some marble chips (in a sock) in your
> filter, and forget about it for several days. Take out the sock when you
> reach the target hardness -- that's all there is to it!
> Adding calcium as CaCO3, vs. CaCl2 or Ca(NO3)2 has the further advantage
> that you are also increasing the alkalinity (KH) and *buffering
> capacity* -- the ability of the system to resist changes in pH.
> If you have further questions, feel free to ask.
> Best,
> George