It's POSSIBLE you have metals since Vit C worked. OTOH, what Leslies did NOT tell you is that Polyquat in large amounts drives FC to 0. When I close in the fall I shock to the appropriate level, then I dump in a quart of Polyquat. In 48 hours, my FC is zero and I then shock to to the approriate level (based on CYA level) and close.

I'm GUESSING you have algae and you need to shock up to 15 and hold it there. Others may say "wait a minute--the clues for metal are too great." I'll concede to their superior knowledge, if so.

Carl