From what I have read on other forums they seem to be the best of all things. go to Reef Central Chem Forum and read all the threads and post on Brightwell and make your own joice, I have no interest here but from what I have read there facts are over rated, and costlier then other things that will do the same, look for Randy Holmes-Farley's articles and answers to these questions.
Randy Holmes-Farley definitely thinks it's snake oil. Something about the PH and the way magnesium dissolves that it will not work properly. As you can tell I am not a chemistry guy, but his articles and posts make it pretty clear that he thinks kalk+2 is bogus. The Kalk part works fine according to him, but he believes the magnesium benefit is bogus.
I guess enough was said, also I have read on other forums Brightwells products that have been tested by Randy HF a scientist/chemist and has made so many DIY chemical additions to are tanks at no monitary benifet to him, are snake oil as well, not Randy's but Brightwells
Efrain now I am not using Kalkwasser because of the calcium reactor but when I used it was Seachem and I had very good results. I can say I am a big fan of Seachem products.
Plse don't let Randy see this thread . It would not be pretty . His explanation of the the product gave you the impression that the magnesium benefit was non -existent .