I don't know that if it's been stated, IMO I have seen in the pass that when you have CAL, ALk, MAG
the biggest thing is ALK when you mess with that you are opening up a huge can of worms like when Moses parted the RED sea. **** hit the fan. lol
ok back on track.
having high CAl isnt so bad other then its going to reek havoc on your pumps for deposits of Calcuim. Magnesium It seems it taks for ever to raise if you are doing it slowly. look at Dez he went through 5 gals of MAG flakes to get his tank up to normal par levels. that was for 1 month.
So slowly bring your ALk up and the rest will take care of its self with some help from you.
I hope this makes sense.
I use a KAlk reactor for keeping my levels in check however, it wont bring up MAgnesium only CAL and ALK, and then you only have to so MAG top up and if you are doing water changes consistently then your mag should be ok.