Acrylic should hold up, I wonder if it was polycarbonate.
BTW, the driveway marker that I used as the stirring rod was attacked by the kalk. I hadn't run the stirrer for a week or so and the orange color from the driveway marker was bleeding into the kalk! I rebuilt using a PVC rod. Kalk is also hard on silicone.
Nylon and PVC are both good to use with kalkwasser.
Hate to dredge up and old topic, but, I built an acrylic reservoir over the weekend out of cast acrylic in clear and white. It was assembled with weldon 4 and it currently leak testing.
Will kalk affect the acrylic? I plan on mixing in a separate bucket and then draining it into the reservoir to avoid precipitate in the ATO container.
In the past I used 5 gallon buckets and never had an issue other than power heads don't last as long pumping kalkwasser as they do in RODI water.