What size tank? How much kalk/day? What kind of calcium demanding animals? What salt mix? How much lighting? (this can affecct your calcium demand by calcification of corals) What ph range? If you want to take the time to answers those questions, you might get more specific advice

Kalk can be spiked with vinegar to increase the saturation rate of calcium; it really works. You can typically get 10% more caclium in your kalk by mixing in 20-30ml of vinegar per gallon of kw. Since this lowers the kw ph, you can also safely does more, assuming you have the evaporation rate.

Big reefer's on to it, though. First you need to raise and balance your calcium and carbonate hardness levels, then maintain them with kw. But, many people do find that kw alone does not meet all the demand for either calcium or carbonate, usually carbonate. so it's not uncommon to supplement kw with a carbonate source; probably the best in this case would be baking soda.

Really the easiest method, IMO, is to use a calcium reactor. Once it's set right, your levels should remain rock solid.