yellow algaeA yellow algae usually appears as yellowish-greenish-brownish spots on the swimming pool walls and floors. Yellow Algae usually forms on the shaded side of the pool. It seems almost "pollen-like" and can be easily brushed off the walls.   It can be found in all swimming pool types. The algae problem will frequently return, if the sanitizer level, water chemistry and pool water circulation are not properly maintained.

Yellow algae has these certain characteristics: It can be brushed away very easily, but returns quickly to almost the exact same location. Although it usually creates a large chlorine demand it has been known to survive in high levels of chlorine (over 6.0 ppm).  Sometimes it can be mistaken for copper or iron staining.

If you already have an algae infestation, take action immediately. Always add algaecides directly into the water, near visible algae growth. The day after treatment, brush walls and vacuum the swimming pool thoroughly and begin using algae preventive.


Yellow algae can be very easy to transfer to another pool, a neighbor’s pool or a public pool, so it is extremely important to remove mustard algae growth from equipment (including the back of underwater lights & ladders) and bathing suits to avoid cross or re-contamination. Pool equipment can be left in the pool during product application or cleaned separately with a mild cleaning solution.