Hey,
thank you Vale! The paper is quite interesting and indeed an answer to my question above.
I think little experiments like yours are fun, although I do not really understand what your result is 😉
In my understanding your filter worked under differnt conditions, is that basicly it?
It is too bad that the canadians did not test aquariums with low pH. But it is really good to know. I will search for more, when I´m next time in the Univertity libary.
Best,
Bennie