How to Treat Mustard Algae

Mustard algae - which is usually a yellowish-green or brown colour, attaches itself to pool walls and other items, including equipment and pool toys. Unfortunately, since it is chlorine resistant, special care and steps must be followed to properly remove this pesky algae from your pool.

Follow these steps to properly remove mustard algae from your pool:

1. Remove all items from your pool (including steps, toys, cleaners, etc); clean steps, toys and accessories outside of the pool to ensure no mustard algae remains stuck to them

2. Using a pool brush, scrub the algae off the sides of your pool walls and also off of the pool floor; once all of the algae has settled on the bottom, run your manual pool cleaner though your skimmer on "waste mode" (be sure your filter is set to waste, so the mustard algae bypasses your sand and/or cartridges)

3. Rebalance your pH and alkalinity levels, ensuring pH levels are between 7.2 and 7.4, and that alkalinity levels are between 60 and 120 ppm; balanced water will help shock work more quickly and effectively - use test strips to check your water chemistry

4. Shock your pool, using twice the amount of a typical shock treatment, brushing any residual algae aggressively to prevent any remaining spores from continuing to grow

5. Run your pool pump continuously until all algae is gone

6. Backwash your sand filter, or clean your cartridge filters to ensure any residual algae spores caught during the continuous run cycle have been removed; if any algae is still present in the pool afterwards, shock the pool again - for pool owners with a sand filter, a sand change may be required

7. Vacuum your pool on "waste mode" using your manual cleaner, or if you have a robotic pool cleaner, run a full cleaning cycle 2-3 times, until all of the algae has been filtered out of the pool; clean your manual or robotic cleaner thoroughly afterwards to remove residual algae spores

8. Treat your pool water with algaecide