I have the DuoClear system - it can't be run without a cartridge in place because of the way it's designed. Instead, I opened up the cartridge, removed the bag full of little balls (this is the silver and mineral I assume), put the cartridge back together and also have not looked back.
Prior to doing this I was getting unsightly brownish stains on my return eyeballs, skimmer basket, pump basket and some on my steps, though not as bad. These stains disappeared with Vitamin C. This upcoming season will be my first full season without the silver/minerals being added. If the stains don't come back, I'll know it was the mineral cartridge causing them.