Add some bleach NOW! You want dark yellow to orange readings while you are cleaning up.

If you can handle muriatic acid, get a gallon and add about a cup to your pool. Wear glass and gloves, watch out for the fumes, put the bottle part way into the water and then open it and pour. Recap it before removing it from the pool, and then dunk it in the pool to rinse off any splatters. Do NOT store the bottle indoors; the fumes destroy wiring!

When it's in your pool, muriatic acid is cheaper and better for you and your pool. But it's harder to handle and store, and more dangerous. But, if you're careful it's fine.

How have you been chlorinating?