The kakwasser stirrer/reactor and calcium reactor are complimentary.
I run a calcium reactor to buffer the water by increasing alkalinity. I run a kalkwasser reactor to add calcium and raise pH. Kalkwasser stirrers/reactors are adding calcium hydroxide to the system. Calcium reactors are adding calcium carbonate to the system. Calcium hydroxide will raise pH but is not a buffer. Calcium carbonate is a buffer.
cya,
Ted