i think taking out Fluoride can be solved with simple chemistry.

I assume that fluoride is present in the form of the F- ion,
then according to the table in my chemistry book, it should react with the Mg2+ ion and become a solid substance(undissolvable)
in the form of the molecule MgF2 Magnesiumfluoride

So what you will have to find is a water-disolvable magnesium-salt.

As a disclaimer:
wach out you dont pour in a substance that is more dangerous than the fluoride you are trying to get rid of in the first place :P