Crews battle algae bloom in Washington's newly repainted Reflecting Pool

Work crews poured hydrogen peroxide into the newly repainted Lincoln Memorial Reflecting Pool on Tuesday to combat an algae bloom, a little over a week after it was repainted as part of President Donald Trump's campaign to revamp some of Washington's major monuments.

National Park Service workers were seen emptying jugs labeled "12% hydrogen peroxide" into the visibly green water of the nearly century-old basin that stretches between the Lincoln Memorial and the Washington Monument on the National Mall.

A spokesperson for the Interior Department said the pool is being treated with "high-tech nanobubble ozone technology" that kills algae, pathogens including E. coli, and other contaminants. The department said hydrogen peroxide is also being used, saying it's "a milder treatment than chlorine" that is used in spas and natural swimming pools.

Christopher Gobler, a professor at Stony Brook University in New York who has studied harmful algal blooms for more than 30 years, said hydrogen peroxide is a common short-term treatment for algae that is not likely to have major health effects on the ducks and geese that frequent the pool.

"It's most harmful to animals that are 100% in the water," Gobler said, adding the chemical can create low oxygen conditions that can be lethal to fish.

It might not be a long-term fix, though, he warned.

"There's always going to be a rebound of the algae," Gobler added. "Hopefully it works as a quick fix, but these algae do tend to rebound."

The reflecting pool was refilled with water starting on June 5 as part of a renovation project directed by Trump that involved draining, cleaning and resurfacing it. The bottom of the pool was repainted in ‌a color Trump ⁠calls "American flag blue."

(Reporting by Ryan Patrick Jones in Toronto; Editing by Caitlin Webber and Bill Berkrot)

Copyright Reuters or USA Today Network via Reuters Connect.

This story was originally published June 16, 2026 at 5:40 PM.