I dose kalk and found these links helpful! 
What Your Grandmother Never Told You About Lime
The Self Purification of Limewater (Kalkwasser)
The Degradation of Limewater (Kalkwasser) in Air
http://reefkeeping.com/issues/2003-0...ture/index.htm
Magnesium and Strontium in Limewater
How to Select a Calcium and Alkalinity Supplementation Scheme

What Your Grandmother Never Told You About Lime
The Self Purification of Limewater (Kalkwasser)
The Degradation of Limewater (Kalkwasser) in Air
http://reefkeeping.com/issues/2003-0...ture/index.htm
Magnesium and Strontium in Limewater
How to Select a Calcium and Alkalinity Supplementation Scheme