I just moved to the Dayton area and found that although the nitrate level in the tap water is near 0ppm, the water is hard/very hard. About a year ago I got an RO+DI unit to remove the nitrates (for the fish) and to soften the water (for my aquatic turtle), and now I'm wondering if I can just use Prime-treated tap water for the fish. I have bolivian rams, cory cats, black skirt tetras, a dwarf gourami, and a BN pleco. Would hard water be bad for any of my fish or plants?