Mustard algae

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
"G", hello and welcome to TFP! :wave: Not so sure that's MA this time of year. Being grey in color, it may just be dead algae. But I'm going to post a some links below which may help. I really encourage you to look at the Pool Care Basics page below, and pay particular attention to the test kit page. If you don't have a TF-100 or Taylor K-2006C test kit already, that really should be a priority before next season. Don't forget to update your signature! :)

Are you closing this year, or do you leave yours running?



Gold Supporter
May 27, 2019
Houston, TX
Having had Mustard Algae for years, that does not look like Mustard algae.

MA is usually found in areas of the pool that are in shade and are not getting as much circulation. It looks like light brownish/yellowish dirt clinging to the walls. For me, it was the walls on the south side of my pool, towards the west. It also showed up in my hot-tub around the area of my step.

While not claimed for MA, the levels for Green Algae seem to be enough to keep MA as bay in the FC vs CYA charts. Stay at the higher end.

As far as using chemicals like Yellow Out, I tried everything. The only thing that worked was keeping my CYA at the lower end of the TFP chart (30 CYA in my case) and dosing chlorine to keep my FC above the minimum line at the end of the day. And my best suggestion is test pool in the evening and dose as soon as people are done using the pool.

If you HAVE MA, follow the SLAM procedure followed by the Mustard Algae procedure.

Here is an extreme picture of yellow algae