Even with kalk, you will still have to supplement calcium and alkalinity.
You can use either Randy's do it your self
http://reefkeeping.com/issues/2006-02/rhf/index.php
or supplement with one of the many calcium chloride products available i.e. Turbo Calcium, Warner Marine, ESV, Reef Complete
and for alkalinity, good old Arm & Hammer baking soda.
Use this handy calculator to determine dosage.
http://home.comcast.net/~jdieck1/chem_calc3.html
Once you find out your tanks weekly consumption rate, you will be able to maintain these levels listed below
Reef Water Parameters
http://www.reefkeeping.com/issues/2004-05/rhf/index.htm