Mustard Algae or Pollen?


New member
May 28, 2020
Chesapeake VA
I have been trying to get rid of some yellowish buildup in my pool for weeks. I don't know how to be sure if it's mustard algae or pollen. I put some clarifier in the water and vacuumed the entire pool and the pool looked great for a day, then the yellow stuff started to appear on the bottom of the pool again. It seems to cover the entire bottom of the pool, with heavier buildup in the angles of the liner and in swirls in the shallow end. It scatters like dust if I move the net over the bottom, even if I don't touch the liner. If it's algae, I'll follow the recommendations to try and kill it. If it's pollen, what do you suggest? It takes too long to vacuum the pool every couple of days. My water balance is good and the water is clear if I don't disturb the stuff on the bottom. By the way, I performed an OCLT and saw no decrease in chlorine levels.
Last edited:

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Welcome! :wave: While you appear to have passed an OCLT, mustard algae (if that's what it is) can still present a problem if not treated correctly. See the link below. Before we go too far down that road though, please clarify what test kit you are using and add it to your signature for future reference. It would also help to see a full set of test results. As for pollen, not much you can do but try to have really good water circulation coupled with a skimmer sock to collect it all.