don't mess with the water
from past experience and my brother's experience (who also tried well water)
the water is too important to fool around with. Use the best water/salt possible. The difference in your tank will be major by starting out with RO or RO/DI. You will have many problems using anything else and trying to "medicate" the water to bring it up to speed.
I bought a Water General (RO/DI) from Barrier and it works great! Can also order on line. Great investment.
Good luck