Calcium tester recommendation?

[Frogger]

I use the Salifert test kit. Works good enough for me.
I have found that I really do not need to test for Calcium. As long as I have a good Alkalinity test kit and I maintain stable alkalinity the calcium level manages itself.

I use two part, but even if you use a calcium reactor or Kalkwasser the balance of Ca to alkalinity (carbonate) is a constant. Your organisms within your tank only use calcium and carbonate in this balance. Ideally you do not want to screw with this balance or get out of balance.