Sounds like you have iron in your water. Since you already have staining, and there is a way to get rid of it (see the sticky in the metals forum), I would go ahead and just keep shocking the pool (back up to 20 ppm!) until the water completely clears up and you're not losing chlorine overnight Once that's done, then you can go through the process to remove the metals stains. You'll have to make a decision, though--you'll either need to add metal sequestrant to the pool to keep the metals from falling out of suspension again, or you need to try to remove it from the water--and the only way I know to do that is to run it through a high chlorine source and immediately through a filter of some sort.

Janet