We've been locked in the "mustard algae or pollen?" debate for about four days, after the bottom of our pool had yellowish drifts, then a powdery coat on the bottom & sloped sides (but not vertical walls) after trying to vacuum the drifts.
On the "pollen" side: Doesn't grow on the vertical walls, settles into circulation-pattern drifts, doesn't feel slimy, FC holds overnight, zero CC, skimmer sock coated with yellow, no worse in shady areas, powderly when dried on cement, and a water sample settled into clear water.
On the "algae" side: Worse after solar cover is on, water slightly yellow, water sample eventually grew green algae, and there is coating on sloped sides.
We tentatively decided it was pollen, and did our regular shock (to 15ppm) last night. Today, the substance was in larger drifts on the bottom than before, again in the circulation pattern. The first thing I did was backwash the filter -- and the water was bright yellow!
Does this say anything definitive about the problem?
I'm planning to test again tonight, then tomorrow and compare to see if FC drops, so I don't have any numbers on that yet. But here are yesterday's numbers, before raising the water level and shocking:
CA (out of reagents, but dipstick shows plenty)
Also: if it's pollen, will slowly sweeping it into the floor filter take care of the problem? (My husband's idea -- he hates vacuuming.)