Im thinking about the top off method but that is only if I need a ATO and that depends on my rate of evaporation. If not then I'll be looking for a stirrer. Deltec makes a good one but good luck on getting parts. I've been looking at the Avast K1.
I was running a calcium reactor on my last reef mainly because of the coral load. For the new system Im thinking on dosing kalk or kalk
via stirrer for the first year or two depending on the rate of coral growth and or coral load. I'll eventually go back to a calcium reactor down the road.