[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re:- Calcium addition

> From: A M Moore <andy at ascot_u-net.com>
> Subject: Best way of adding Calcium ?
> Could someone advise me of the best way of adding Calcium to my water ?
> I have used Calcium Carbonate before but it is virtually insoluble. I have
> heard of using Calcium Hydroxide or Calcium Sulphide. Is there anything
> better I could use ?

	If you use finely ground calcium carbonate, it will dissolve
slowly to form the bicarbonate in solution, which is what you want, if
you are after GH and KH.  Calcium hydroxide will work, producing the same
result (the bicarbonate), but it will use twice as much CO2 in doing it,
and will do it _very_ quickly, so you may well get a huge pH spike.

	CaCO3 + H2O + CO2 -> Ca++  +  2HCO3-   (slow, because CaCO3 is
pretty insoluble)

	Ca(OH)2 + 2CO2 -> Ca++  +  2HCO3-   (very fast, because the Ca(OH)2
is quite soluble)

	Calcium sulphide would dissolve, producing S-- ions in the 
water (on second thoughts, probably more HS- than S--), killing
everything in the tank in very short order.  I suspect you meant
to suggest the sulphate, which will dissolve (slowly, again), giving
GH but not KH.

	I would use the powdered carbonate.  Calcium chloride will work
quickly, if you really want that, and don't mind the Cl- ions in there.
The chloride will, like the sulphate, give GH but not KH.

Paul Sears        Ottawa, Canada