Water chemistry
Mustard algae
Mustard algae is a yellow-brown algae that clings to shady walls and resists normal chlorine.
Mustard algae looks like sand or pollen on shaded walls and steps. It brushes off easily and then returns. It resists normal chlorine levels, so a standard dose often fails.
It can also live on swimsuits, toys, and brushes, so treat those along with the pool. Brush the pool, apply a strong shock or a mustard algae product, and keep free chlorine high for a few days. Clean the filter after. If it keeps coming back, test your chemistry and consider a professional treatment.
Related terms
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