reconstitution of, affects of RO water

   Many people seem to find tap water beneficial to the grawth of their
plants as a source for some trace elements.  As a discus and South American
dwarf cichlid keeper I use only RO water reconstituted with Kent's RO Right.
 I started doing this with only the fish in mind.  My questions are: 1.what
is the  affect of using RO water with plants (does anyone have experience
with this) and 2. is there a method of reconstitution that would be
formulated with both the fish and the plants in mind?
    These questions were spawned by the discussion on the importance Ca and
Mg.  My RO unit affectively eleminates both of these from the water and I do
not know what all the RO Right adds or in what amounts.
        Thanks, Nathan