Black is hydrogen sulfide. Sulfur, rotten egg stuff. Bacterial iron is, best way I can describe it, take the lid off the toilet tank look in it, if it looks like orange pond scum you have bacterial iron. Bacterial iron wont turn colors until it gets oxidized (toilet tank), fill a glass and let it sit on the counter overnight. If its not orange when you fill it, but orange in the morning, then, bacterial iron. Both Problems are temporarily fixed by shocking the well. If you have a softener put it in by-pass, the bleach will kill the resin. If you have a drinking water system or fridge filter turn them off, the bleach will kill them too. I will PM you my # free advice anytime.