US President Donald Trump in April ordered the Lincoln Memorial Reflecting Pool to be painted "American-flag blue" as part of a renovation of the Washington landmark.More than $14 million later, the famous rectangle is instead a deep shade of American dollar green.Within days of the paint job on the 618-metre-long pool, clumps of algae started to appear and quickly proliferated under the summer sun.The setback has left workers scrambling to clean the shallow pool and get it back to its desired deep blue colour in time for America's 250th anniversary on July 4.Like most things in Washington, Mr Trump's order to paint the pool and the reaction to it turning green have sparked controversy.The initial issue was that he awarded the main contract to his "pool guy" without putting the lucrative award out for competitive bid. He initially said it would cost less than $2 million, but the amount skyrocketed.The historic pool, built in 1922, has experienced algal blooms over the years, and other presidents have tried to keep it clear. It only reaches a maximum depth of 76cm; bird droppings accumulate in it, and it is sometimes filled with river water that already contains algae, making it look more like a pond than a reflecting pool. Ducklings swim through algae which has built up at the newly refurbished Lincoln Memorial Reflecting Pool. EPAInfoTo try to rid the pool of its green hue, workers are pouring hydrogen peroxide into the water and deploying what the Department of the Interior calls "high-tech nanobubble ozone technology"."This technology is actively killing algae, pathogens (e.g., E. coli), and contaminants that have long plagued the Reflecting Pool," a department spokesperson said in an email, adding that hydrogen peroxide has no harmful side effects for marine life or the environment.Water flows back into the Lincoln Memorial Reflecting Pool on June 4, 2026 after renovations are completed. Thomas Watkins / The NationalInfoThe representative also blamed a Barack Obama-era renovation for being too expensive and causing previous algae outbreaks.A man who identified himself online as John Bell, a professional pool cleaner, said the fixes wouldn't work because the natural filtration system of the pool's stone floor had been sealed.On Tuesday, a stream of tourists was snapping pictures of the pool and efforts to clean it. William and Connie Maier, from Albuquerque, New Mexico, had come to Washington on a Harley Davidson, travelling almost 6,000km via Florida specifically to see the reflecting pool.They said it was "absolutely" worth the eight-day ride. "I feel enlightened and happier because it's turning blue the way it's supposed to," Mrs Maier said."They've cleaned it up in the last 24 hours, I think it's going to be American-flag blue within the next few days," her husband added.