How do you know you need to dose?
What are your parameters for calcium and alkalinity and how do they change from one water change to the next?
Animals that build calcium carbonate skeletons need certain levels of calcium and alkalinity in the water for healthy growth. You measure these levels by testing. If you find your water changes don't keep up with things then you need to start some sort of dosing. You need to be testing for calcium, alkalinity (and magnesium) to know if you need to dose at all.
If you do need to dose, two part dosing systems are simple to use. You know if you need the pH up or down one by testing your pH (as well as the other three parameters).
You can DIY two part dosing chemicals.http://www.advanceda...004/4/chemistry
Another alternative is kalkwasser. You can add kalk with your top off water. Kalkwasser is only good for maintaining levels and should not be used to raise them. You need to use another method (like two part) to bring things to a good starting point.
Whichever dosing system you choose, you need to test to know how much to dose and at what intervals to avoid parameter swings. Buy accurate test kits.