With minerals, it shouldn't make too much of a difference. Skimmers are designed to pull out organics that stick at the air-water interface. Ions like trace elements, Mg, Ca, etc, don't have this tendency, so they should not affect the skimmer, nor should the skimmer tend to pull them out.
Won't hurt to turn it off, though.
Just a reminder that dosing with traces should be done carefully. They are needed in tiny amounts, and many can be toxic if too much is added.