You can but it's not the greatest means of supplimentation. In your case though it won't help. Kalk
raises both alkalinity and Ca
equally so the imbalance will remain. You need to focus on adding a Ca
only product until the levels are correct. If approaching this from a water change aspect, tweek the change water with a CaCl
additive to balance the levels and then use the kalk
by dripping at night into the tank. Kalk
should only be used once the levels are balanced as a means of maintenance.