What it sounds like is that you have iron and manganese in your water. Both of these can be removed with either a water softner or a Greensand unit. Depending on the amount of iron and manganese will determine what system is best. The best solution would be to have your water tested by a water conditioning company in your area.
I work for a water conditioning company in NJ, different parts of the country have different water problems, you need to find out what exactly is in your water before you can correct it. If you have any further questions, feel free to e-mail me.