So, I've been using B-ionic for quite a while on my tank (a few years). I wondered, would there be any reason to change to kalk or add start adding it to my topoff in addition to the b-ionic?
Is it a one or the other thing? Or, should I do both??
To answer the question you can use either or both. IME kalkwasser is generally a bit more limiting due to the pH raising effects and being constrained by evaporation rates.
Bionic is a more complete solution then Kalk, which only provides Ca and alk. I would use Bionic, Cbalance, or the bulk stuff from TwoPartSolution (based on Randy's forumla IIRC) for the primary additive and use Kalk if you need more Ca, alk, or higher pH.