I decided to move away from Kalk. I started with kalk in the spirit of simplicity, but i've decided to stop with it, also in the spirit of simplicity...
I don't have the space or desire to mix up huge batches of kalk, so I decided when setting up this tank to use the Avast Kalk Stirrer. It's designed well but I was seeing a lot of fluctuations in alk and ph, and just generally struggled to get consistent saturated kalk out of the thing. The idea was to monitor it with a PH probe, but those probes can barely be trusted on good days, and when exposed to such high PH all day I found it quickly de-calibrated and wandered all over the place and was generally useless. Dosing kalk also consumed two dedicated outlets - one for the versa and one for the stirrer, so it'll be nice to get those back.
I switched to ESV 2-part and already appreciate the consistency. I measure alk twice a day with the Alkatronic so it's nice to be able to judge alk consumption now without just wondering if it's the kalk's saturation wandering around...
One less piece of equipment and 2 fewer outlets is a win too. Maybe once my tank is consuming enough alk that I can replace the ATO with kalk I'll go to mixing it traditionally into the ATO and pumping it to the tank via versa, but for now I think ESV is the way to go...
PH is still ~ 8.05 - 8.35 without Kalk and I'm good with that.