I just want to second the don't get hooked into BioGuard advise... I actually have a mineral springs unit I bought on ebay for $86, and have never used a drop of bio guard products... I stick with Muratic Acid, Leslies CYA and this year, I do have to add a bit of calcium. I buy my salt from Home Depot, Morton Coarse Solar salt.... this works well.... don't get caught up...get educated...