SPRINGFIELD, Mo. (KY3) - For area pool owners, unwanted guests are never welcome. While a particular problem like mustard algae and others can occur at any time during pool season, James Blevins ...

The algae spores are in the air, and if enough of them end up in your pool, you get mustard algae. Pools that have high levels of sanitizer (chlorine) also get mustard algae.

Answer: This pool could still have algae even with the water testing fine. It may have mustard algae, which brushes off in a cloud of dust, or a resistant strain of green algae.