I've going to say you dont need to soften their water, most water suppliers list soft water as medium/hard when it's still below 200ppm.
Its the livebearers you will probably have to harden their water.... they need it over 200ppm
Example.
My water supplier claims our water is "moderately hard".
But my GH is 90-150ppm, which is soft range for fish! Pygmies are fine in this range, but livebearers are not.
So i have a bit of cichlid sand in a pouch in my filter to raise my GH slightly to 200ppm for my livebearers.
Ah right! Ok, so I will get the exact water number but most likely I need to harden it for my live bearers....hopefully I can get something from Amazon or my local pet shop can order me something.