I thought you might have built one already it was an old post that Iread. Does the home built one work very well? They look like a complicated piece of hardware.
there quite easy to build as long as you have some basic diy skils. basicaly you have a chamber with water flowing through it (by pump mounted on side) then you have two inlets and one outlet.
inlet 1 - CO2
inlet 2 - tank water
outlet - water out
the CO2 makes the water acidic which reacts with the "lime" type media causing it to disolve.
I am a machinist by trade so diy is not a problem. I don't know if I'll ever get that serious as to need a calc reactor but you know how this hobbie goes. You always want something more something better. I'll just have to see how addicted I get to this stuff.