5 Steps to Kill Mustard Algae in a Pool

Shock at triple the normal dose Raise free chlorine to 15–20 ppm and hold it there for 24–48 hours. Normal shock levels won’t work because mustard algae is chlorine-resistant.

Brush every surface daily You must physically break the biofilm so chlorine can penetrate. Focus on walls and floors where the yellow dust settles.

Run the pump 24/7 Continuous circulation keeps the chlorine distributed. Backwash or clean the filter regularly to maintain flow.

Use a mustard algae algaecide It helps but is not a substitute for shocking and brushing. Apply it according to the label after the chlorine level drops.

Don’t let up for at least a week Mustard algae returns if you stop early. Keep shocking and brushing until the yellow is gone for seven straight days.