Re: Calcium requirements in water

> From: spush at saudan_HAC.COM
> Date: Thu, 06 Feb 1997 16:18:13 PST
> I never really got an answer in my quest for an optimal or
> safe minimal value for Ca concentration but since a common GH
> hardness target is 4-6, I figured 40 mg/L would be a safe
> guess.

If a "common target" is 71 to 107 mg/l (4-6 dGH), why is 40 mg/l a
"safe guess"? 

A "better" answer is to meet the requirements for the fish you are
keeping.  For example, if Rainbowfish are kept in water that has low
GH, they develop open sores and other maladies.  

40 mg/l might be fine for plant growth but 2+ dGH is a little low for
community tanks.  I would suggest 100 mg/l or ~5 dGH as a general
guideline and only go lower if your fish require it. 

George in Snowy and Slippery Colorado