Is this mustard algae?


LifeTime Supporter
Aug 19, 2014
Pacific NW
It looks a lot like pollen...I've not had nearly that much as you, but I know it's pollen since
my test results are good and my water is crystal clear.

Is it on the side walls too? hard to tell from the photo.
If it is, it could be mustard. I dealt with it once in a previous pool and
it was yellow, not green.

Do you have a proper test kit? (K2006C or TF100)
Can you post some test results?

You should prepare for a SLAM if you want it cleared up any time soon.


Gold Supporter
Jun 28, 2017
Fresno, CA
Both pollen and algae will stress your sanitation program, and eventually foul your pool. For both problems the answer is free chlorine, FC. How much you need depends on the contaminant and your current stabilizer level. You must be able to measure several components of your water chemistry in order to properly manage your pool system. Start here for some good information.....TFPC for Beginners

The conclusion sums up the situation we all face with managing a pool or spa.....


The leading cause of pool problems is simply ignoring the pool. Your pool is like a pet: it requires constant attention. The number two cause of problems is adding chemicals you didn't need and don't want. Not only do these extra chemicals tend to cost a lot but they can also cause problems.