You should adjust your calcium and alkalinity so that they are at proportionate levels, then dose daily/weekly/whatever with a 2 part mix that is in the correct ratio. It may be that the products you are dosing with do not balance out and you end up with higher calcium levels than Alk levels. If you balance the two with additives, then dose equal amounts of both, you should stay on track. Calcium carbonate that precipitates on heaters and pumps is equal parts calcium and alkalinity. Coral also uses these two in balance. This is why using the two part system with both in balance with one another works. Kalk has the same balanced ratio of Calcium/ Alkalinity, and when using it, you will not be adding chloride ions that the two-part solutions contain. It's the best, cheapest method by far for low-medium demand systems, but will not keep up with a high demand... it can also be messy, as the solution will harden the lines in peristaltic pumps and can easily raise pH to dangerous levels if added too quickly.