well since i know "labman" i will jump in here a bit
first off, you are not at a stage where you need a reactor.. yet...
your calcium needs are still low where you can keep them in control with water changes and minor dosing.
but as your needs grow you are goign to be in the same position as me..
i am currently dosing
kalk in my top off water (which coul be your next step as needed) but this is getting to the point were it wont be enough.
i am gurrently researching a
DIY nelson (kalk) reactor or a
DIY calcium reactor.
i havent come to a desicion yet so we'll see soon...