I have and do use aragmilk for supplemental Ca and Alk for my customers who will not or are not able to use kalkwasser. I also use aragmilk for RoDi reclaim for the few freshwater tanks I take care of. Only real problem is the people who wont are cant use kalkwasser, also wont use the aragmilk regularly, and often fail to add thier make up water as well. So I go and do it for them and charge them for it as well. LOL I like aragmilk it does tend to clump up inside though and needs to be shaken a LOT!!!!! before use. It clears up after use in about 20 mins or less. Its not a bad product in my experince. I know nothing about purple up. Steve