Every tank is different, but a lot of tanks have trouble getting enough calcium and alkalinity with only Kalk. If budget issues are a concern, then the two-part is inexpensive and definitely can handle the load. On the other hand, Kalk as ATO works well for a lot of people, and can help with the pH. I don't know what the cost of a dosing pump would be these days, but there are a number of vendors selling peristaltic pumps that should work well. You might want to price out the equipment for Kalk, and work from there. If you're interested in automating the two-part, a two-channel pump should do the job.
