Kalk/Ca reactor

[BCOrchidGuy]

I've read through hundreds (yeah honest) of previous posts trying to find a simple answer to the question, when is a kalk reactor better than a Calcium reactor and when do you absolutely need the Calcium reactor.

If you're dosing your kalk through your freshwater top off and it's keeping your calcium at an acceptable level then kalk is the way to go... (am I correct?)

If dosing kalk through freshwater top off can't keep your Ca level high enough you'll need the Ca reactor.

How confused am I?

Doug