Turbo36 is right on the money. I have the same problem and the fix is to shock the well with bleach. Follow Turbo36's directions and you can live with the problem. I have been shocking my well for about 35 years I tried an iron filter in front of a softener after we first moved in to our place and it worked no better than a softener alone using salt made for wells with iron in them (usually in a green bag). Note the newer softeners use very little salt. You may have to clean out the drain pipe once in awhile (I clean my pipes every 12 years or so). Oxygen is the catalyst. Until Oxygen comes in contact with the Iron Bacteria in the water you only get the black slime which is not much of a problem.