There are many forms of CA supplamentation available to the hobbyest these days. IMHO, Kalk is the easiest, cheapest and the best, but if you don't want to get into the "hassle" of Kalk, you might consider a product like ESV's B-Ionic. It will add both CA and buffer the ALK in a balanced formula with it's two part addative. You can have a perfect CA level, but without a balanced ALK, it does no good.