Trump administration uses hydrogen peroxide and tiny bubbles against algae in Reflecting Pool

Members of the National Park Service clean the Lincoln Memorial Reflecting Pool of algae, Tuesday, June 16, 2026, in Washington.

WASHINGTON — U.S. President Donald Trump’s remodelled Lincoln Memorial Reflecting Pool with its “American flag blue” bottom has turned chartreuse from an algal bloom that park service workers struggled to address Tuesday just days after its more than US$14 million renovation.

The Washington Monument is once again visible in the refilled pool, but Trump’s vision of an azure expanse between the D.C. landmarks has been complicated by the harsh realities of chemistry and biology known to any backyard pool owner.

The work has been confounded by the unique challenges posed by the scale of the structure, bigger than 10 Olympic-sized pools — which Trump has called a lake — and the source of its water: the often-fetid Tidal Basin.

Algae has plagued the site since it opened more than 100 years ago, but Trump set his sights on addressing it as part of his aggressive push to beautify Washington as the country approaches its 250th anniversary.

Contracts worth at least $14.8 million have been awarded for the project, announced in April by Trump, who said he was inspired by complaints from a friend visiting from Germany who called the pool dark and disgusting.

Teams of National Park Service employees and contractors deployed chemicals and ozone nanobubbles Tuesday in a bid to keep the algae in check, not dissimilar from efforts to clean the pool before Trump’s renovation kicked off.

“What do you expect?” asked Cochise Wanzer II, president of the Pool Service Company in Arlington, Virginia. “You’re basically taking natural, untreated river water, pumping it in and expecting it to do something different from what it would do out in the open.”

And the new coat of paint on the bottom of the pool has added an additional twist to ensuring the cleanliness of one of Washington’s most memorable destinations: “Now that the bottom is nice and dark, it elevates the temperature and the algae grows better,” said Wanzer.

The chemicals and ozone nanobubbles — a water purification treatment used to avoid some harsh chemicals — were one part of the effort underway to clean the Reflecting Pool.

Workers used a swimming pool-type vacuum cleaner to suck up algae from the bottom, leaving behind clean patches of American Flag Blue paint adjacent to enormous swaths of green algae in a pattern familiar to anyone who has ever vacuumed a carpet before.

The park service said in a statement it is also using hydrogen peroxide, a milder treatment than chlorine and one used in spas and natural swimming pools. “There are no harmful side effects to marine life or to the environment,” it said.

As the mitigation work continued, a contractor took off his socks and shoes and rolled up his pants to his knees and proceeded to wade into the pool to place an ozone nanobubble tube as tourists and locals milled about on a sunny morning.

Rick and Ariana Pettit, a couple from Las Vegas who are road tripping in their RV across the United States, posed for photos at the iconic site of protests and marches as cleaning continued. Dressed in American flag-themed leggings and a Make America Great Again leotard, Pettit remarked to her husband, attired in an “Veteran for Trump” American flag button-up: “Look, it’s already looking more blue.”

Wanzer was blunt in his assessment of what it would take to maintain the pool as an algae-free space: “They may want to drain it, hose it all down, and start from the beginning with fresh water and treat it as the water comes in.”

Katie Vogel And Jacquelyn Martin, The Associated Press