The nanobubblers had to go.

It was early June, and the Trump administration was planning an event at the Lincoln Memorial on June 12 to promote President Trump’s Ultimate Fighting Championship birthday celebration at the White House.

Dotted around the perimeter of the memorial’s Reflecting Pool were the nanobubblers, the temporary water-purification machines meant to keep the pool clear of algae. Encased in black fencing and powered by large generators, the machines were something of an eyesore.

Before the event, the National Park Service asked Greenwater Services, which won a $1.7 million no-bid contract to install the nanobubblers, to remove them, according to two people briefed on the decision. The people asked for anonymity because they feared retaliation from the administration. The Park Service did not provide a reason for the removal, but it coincided exactly with the promotional event, which drew crowds to the Reflecting Pool.

Photos from that evening showed the pool without the hoses or enormous machines working to keep the water clean. The water looked dark blue.