Mollies and other livebearers will be fine in the water from the garage pump. GH of 300ppm is not a problem.
That brings us to the softer water. It seems as if there is a softener involved, and that can be dangerous for soft water fish if it uses sodium salt to replace the hard mineral salts.
That brings us to the softer water. It seems as if there is a softener involved, and that can be dangerous for soft water fish if it uses sodium salt to replace the hard mineral salts.