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.