Here are some good links to read through as this will give you a better understanding of water chemistry in aquariums:
http://www.canreef.com/vbulletin/showthread.php?t=19425
Also, I'm not sure why you are dosing Kalk if there is nothing but cycling rock in the tank...
Kalkwasser is a very basic solution that will raise pH. The solution itself has a pH of around 12 or so. You drip it at night because the pH of the water in the aquarium drops at night due to respiration of the corals and other photosynthetic organisms in the tank. So to create a more stable pH (in the 8.0-8.2 zone) you drip a high pH solution into the lowered pH solution to bring it back up.