How do you maintain your MAG / CALCIUM levels

[Lampshade]

I use ARM media and even with their new high Mg mix i notice i'm usually still only at 1100-1200 ppm Mg. It may be the same as with Ca/Alk where a calcium reactor will maintain levels, but building them individually will never work. I just started adding Mg, i'll see how everything stays balanced for the next while before adding more.