Reverse Osmosis water(RO) and Distilled water(DI) have all of the elements removed and are truly "flat". One needs to add minerals and substances to the water to bring it to proper levels. I do not worry about these things as I use tap water for almost all of my tanks. Tap water has a nitrate reading of about 5, nitrites 0, pH of 7, ammonia 0. Thats all I worry about. I have never tested for anything else. I do have a RO unit in the basement that is used for some of the breeding tanks, but those a scant in number. These tanks are usually dedicated to my "experiments".
So, if you intend on using tap water, check it and forget it. It is what it is. If certain readings are a tad high you may want to treat your water before adding it to your tank. I speak specifically of nitrates, nitrites, ammonia, choramine and chlorine, maybe pH if it is too high or low. Some of those you definitely do not want in your drinking water, let alone your tanks. But, generally, it is what it is. I have a friend that has tap water pH of 8.2. He now keeps African Rift Lake cichlids. Perfect.
Use a liquid reactive test kit and not test strips. More accurate that way.