Aragonite for Calcium

["John T. Fitch" <JTFitch at fitchfamily_com>]

Until I used it up, I've been adding a little CaSO4 (gypsum) to my tank
after each water change to boost the Ca level up into the recommended
range of 25-75 ppm.  I had bought the little bottle from a home brewery
store at what seemed to me to be a very high price.  So, since it's gone
now, I was wondering about using something else.  At the LFS, I found
Aragonite, which is very cheap.

According to one web site on minerals, the chemical formula for Aragonite
is CaCO3, calcium carbonate.  That sounds great.  I could put some in a
bag and drop it into one of the compartments in my canister filter.  That
would boost both the GH and the KH and maybe I wouldn't have to add
NaHCO3.

But the next line said "sometimes with some strontium, lead, and zinc."
Does that disqualify it?  Thanks.

John T. Fitch
Web Site: www.fitchfamily.com/aquarium.html