With some help from Swim University and our own Robert Sparks, we can tell you what this stuff is and the best way to get rid of it!
First things first, identify your attacker.
This stuff is most seen in warmer southern areas. It does not react to chlorine and can even live on your bathing suits and pool toys. Algae grows in tiny microscopic clusters and keeps itself alive through photosynthesis; so pools are especially prone to any kinds of algae. The best prevention for algae is to have your pool regularly feeding chlorine and a nice chemical balance.
Pollen can also be mistaken for mustard algae so try to brush the stuff away and if it sinks to the bottom or towards the main drain it is most likely pollen. Check your chemistry and if the chemistry is perfect and the stuff tends to float away you more likely than not have some pollen.
Clean items that live in the pool.
Once you have identified you have mustard algae, take everything out of the pool and use bleach or another powerful cleaner. This goes for bathing suits and pool toys.
Vacuum, Brush, Shock, Algaecide, Repeat.
First you want to manually vacuum your pool to waste. The filter might have algae as well so vacuuming through your filter will only make things worse.
Brush the walls, steps, etc. Scrub hard or else you might have to do it all over again! This stuff is tough!
Shock, shock and more shock! (Three pounds per 10,000 gallons) Dump the stuff all around your pool (making sure not to have it spread up on your pool deck or you will stain it!) Leave your filter and pump running 24 hours a day until the algae is gone for proper filtration. Depending on how bad the algae is, break down your filter by taking it apart and clean the grids. Do this step before running your filter 24 hours.
Putting a mustard algaecide like this one is a good idea, especially since mustard algae is close to non-reactive to chlorine (shock is very concentrated chlorine). Algaecide guarantees to clear the algae and leaves no room for error.
Continue to brush!
Shock again in a day or two!
Continue to balance and maintain your normal chemistry to keep the algae at bay while you try to kill it.
This is important so the algae does not try to attach itself to the walls and floors again.
Once the chemistry is regular and the pool looks clear - you’re done!
Prevention
Prevent any more algae from coming back by:
- Ensuring good filtration and running your pump for 8 - 12 hrs during the season
- Proper chemistry balance
- Regularly brush and vacuum
- Most importantly: Enjoy your pool!