I'm using RBS currently, I switched from IO which I was supplementing with zeomag (in my reactor) and of course my ca reactor. Thing is my potassium levels were low. At the time everyone was all hoo haa about potassium. My tank doesn't look any different (granted, I'm using zeo so technically it does look different but who knows if thats zeo or potassium
). Anyway, supplementing with all the various stuff was becoming a pain so I switched. All my levels are happy now. I found IO to be low in Mg and K but alk and ca were fine (Sr was also low but...whatever). Anyway, I've tried IO, Kent, Seachem and now RBS. So far RBS has been the best bang for my buck however when I run out and am not near J&L to get it likely I'll be back to IO as I hate paying shipping for salt.