I have noticed what I thought was black ash on the surface of my pool. I thought it was ash because it occurred the day after we had a major windstorm and I had left our fire pit uncovered. My assumption was that ash had been blown into the pool. However it has been 3 or 4 weeks and I continue to see it even after thinking I had skimmed it all. I do not see it on the walls of the pool, just on the water surface. Anyone have any idea what this might be? Could it possible be Black Algae? We are in the cold weather season so I would not expect it to be algae but I’m out of guesses. Recommendations on how I should treat this?