I use Seachems Reef Advantage for Calcium...and Seachems Reef Builder for Alkalinity. Both have effectively established desired levels. To help maintain my levels I drip kalk 24/7.
But I'd say bang is correct...a calcium reactor(expensive) is probably the "best"...
I also use seachem's reef advantage calcium (powder) it raises very effectively. I think I might try an ionic balanced liquid when I run out though like b-ionic or kent makes a similar product, I forget what its called. Only b/c of the constant balance b/w calcium & alkalinity.
Kyle