I kept on with kalk after going zeo. I don't know if it was bad or not.
I think the only way to really find out if it's for you or not is to try it for about 6 months or so. It's the best way to find out if the extra work is balanced by the results. Having said that, I thought the extra work wasn't that much extra and the results were pretty impressive. The most impressive change I thought was how much the water got polished clear. It's like your lights get 20% brighter. Totally subjective, of course, but I first thought something was wrong with my lights because they seemed so much brighter all of a sudden.
