4 Steps to Kill Mustard Algae in a Pool

Raise chlorine to shock level Shock the pool to 3–5 times the normal chlorine level for your algae type. Mustard algae is chlorine-resistant, so standard doses won’t work.

Brush every surface with a nylon brush Scrub the entire liner, including corners, behind ladders, and under the skimmer. Use only a nylon pool brush—wire brushes or abrasive pads will damage the liner.

Run the filter continuously Keep the filter running nonstop. Backwash or clean it when the pressure gauge rises.

Repeat the shock-and-brush cycle as needed One round often isn’t enough. Repeat the process until the algae is gone. Skipping the brushing is the most common mistake.