Add a sequestrant before you shock.

Yes, you need a sequestrant — and hold off on the shock.

If you dump chlorine or shock into high-iron well water, you’ll oxidize that iron instantly and get rusty brown stains all over your pool walls and floor. That’s a pain to fix. Instead, start with a metal sequestrant (sometimes called a chelating agent or stain preventer). Brands like Metal Magic, Pool Mate Metal Control, or any pool-store product labeled “for metal removal” will do. Add it according to the label, run your pump for 24 hours, then test and adjust pH and alkalinity to normal levels.

After that you can balance calcium hardness and finally shock the pool. If you already see stains, you might need a stain remover (often based on ascorbic acid), but the sequestrant should prevent new ones. Just keep an extra dose handy — every time you add fresh well water, you’ll need to treat it again.

Better to prevent stains than scrub them off.