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Re: Aquatic Plants Digest V3 #1068, Calcium additions

Hey George thanks for putting up with me - the chemically inept!
Also Jamie Johnson sent me some more good info about Ca/Mg additions and how
to calculate what you have/want!

Tom Brennan

-----Original Message-----
From: George Slusarczuk <yurko at warwick_net>

|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
|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.
|> Date: Wed, 2 Jun 1999 17:29:51 -0400
|> From: "Tom Brennan" <brennans at ix_netcom.com>
|> Subject: Re: was APD V3#1063 & Calcium Deficiency
|> George wrote........
|>  Mon, 31 May 1999 16:12:40 +0000
|> From: George Slusarczuk <yurko at warwick_net>
|> Subject: Re: Aquatic Plants Digest V3 #1063
|> Hello Ken,
|> Calcium chloride works well, but will acidify your water.
|> Marble chips (used in landscaping) in the filter will keep calcium
|> carbonate at saturation level.
|> Dolomite (sometimes used as gardening lime) will also add magnesium to
|> the water. Magnesium is needed for chlorophyll formation.
|> Best,
|> George
|> ============================================================

Then from Jamie Johnson......"I keep my Ca around 30ppm and my Mg around
10-15ppm, and
> that keeps my GH around 6-7 degrees, perfect for me. (Handy equation -
> (2.497 x Ca conc.) + (4.118 x Mg conc.) = hardness in ppm. 17.9ppm
> = 1 degree GH). "
I Wrote back.............
> So for me (Mr. chemically inept), using your equation how do I figure the
> and Mg concentrations?
> Taking your Ca/Mg numbers and plugging them in you get:
> (2.497 x (Ca of 30ppm)) + (4.118 x (Mg of 15ppm) = 136.68 (hardness in
> ppm)????  = 7.635 gH???

Jamie....Right!  (2.497 x 30) + (4.118 x 10 {actually my level}) = 75 +
41=116, thus 116ppm/17.9 = 6.5GH

Me again..... Right now in my 125g my kH is <2 and gH is <2.  How would I
figure what to
> add to get my gH to say 4 or 5?
>                 kH                               gH
> (2.497 x (2x17.9)) + (4.118 x (2x17.9)) = 236.817(hardness in ppm)????  =
> 13.23 gH???

Jamie......Not exactly. GH of 5 = 17.9 x 5 = 90ppm total hardness. We'll
say Ca = 20, then 2.497x20= 50ppm Ca hardness, so you need 40
ppm Mg hardness to equal 90ppm total hardness. 4.118 x ?=40,
then Mg level needs to be 9.7ppm. Plug them all back in:
(2.497 x 20) + (4.118 x 9.7) = 50 + 40 = 90ppm total hardness, or
5GH. To work it backwards, you need a known amount of either Ca
or Mg to calc. how much of the other to add. The KH is a little
more tricky, I know 1/4 tsp. to 3 gal (11.5L) will give me ~65ppm
alkalinity + the 15ppm in our water (0.8 KH), for a total of 4.5 KH
(80ppm alk.) If you have a test kit for alk, start with this and you
should get these levels and you can adjust it from there. A little at
the time is better for baking soda, cause it really swings the pH. If I
had no CO2 supplement, my pH would be 7.6-7.8 for 2-3ppm CO2
in ambient water. Also, if you had CO2 to 15-20ppm with 1KH, the
pH would be ~6.0-6.2 :-(. So, it's important to bring them up
together so the pH stays reasonable. 7.8 is alot better than 6.2, so
I would definitely get the alk straight before adding CO2. Hope all
this helps. If you need anything else, let me know.

Hope this helps someone out there!