Ash in air making pool water green


Well-known member
Jun 14, 2012
Blaine, MN
Hi, The pool guy was out today and warned me that he's had 20 pools go "green" because of the ash in the air from the forest fires out west. He recommends adding "filter aid" if I experience any green and the chlorine looks good. Any thoughts?


Active member
May 13, 2016
I think it's more likely that they are going green because it's May and the water is warming up. That said, ash will contain significant amounts of phosphorus, which will turn into phosphate in your pool, and that can lead to algae. However, if you keep your FC at the right levels, the increased phosphate concentration shouldn't be a problem.


TFP Expert
Feb 3, 2014
Central Minnesota
Well... not sure that makes any sense. If ash were to fall directly into the pool, you'd expect a rise in pH. Nothing more. Aside from a pH change, wood ash contains nutrients. I think this is a good summary here without getting to nuts about details: Bulletin #2279, Using Wood Ash on Your Farm | Cooperative Extension Publications | University of Maine Most of the content is calcium, not an algae nutrient. The only potential nutrient is phosphorus, but that's fairly low on the list of contents.

You can also see there that there would be trace amounts of metals in the ash but it would take A LOT of that ash to make a meaningful increase in metals when the concentration of that ash is estimated at 1.5 pounds (copper) per 5 tons of ash. 1 pound of ash would have roughly 0.07 grams of copper... If a pool already has copper in the water, a rise in pH due to ash going in the pool would actually make the copper more likely to precipitate into stains. A decrease in pH will cause stains to dissolve in the water, making it green.

Chalk this one up to another pool guy red herring, in my opinion.