I stopped using dolomite, oystershell, or aragonite a couple of years ago, and replaced any potting mix system with new mix that was absent for these materials.
I also add back 10% well water to my daily watering/feeding regime. As per Justin's observations, most surface and ground waters will have more than enough Ca (and Mg).
I've measured the hardness, calcium, and magnesium concentrations that comes in from the well water and fert, so I know there is more than enough Ca and Mg in my water to exclude adding any more solids into the mix.
If you are after pH control then that's' another matter altogether. Need to watch alkalinity (bicarbonates) not calcium for efficient buffering of acids.
Your well water probably also has plenty of bicarbonate alkalinity to counter pH drop as long as excess N isn't getting into the system and you are just feeding bacteria. It's amazing how much pH drop problem is eliminated when you cut back on large episodic feedings (i.e the "weakly weekly" approach) and just trickle in tiny amounts on a daily basis.