The Lincoln Memorial reflecting pool is like a Petri dish* for algae.
Donald Trump had the pool contractor who works at Trump National Golf Club in Sterling, Virginia, recoat the Lincoln Memorial reflecting pool Old Glory Blue, which he called "American flag blue." Trump said the people who did the work were "patriotic." The company got paid $14,191,477.48 for the work. Trump is a hack real estate developer from Queens, New York, not a master builder. He knows nothing about reflecting pools. The pool became filled with algae 5 days after being refilled, showing what happpens when people don't know what they're doing.
A nanobubbler ozonification system was supposed to ameliorate the problem with algae in the pool. It didn't.
The pool has had chronic problems with algae since being switched from municipal water to water from the Tidal Basin in 2012. Municipal water is clean and chlorinated. Tidal Basin water is full of algae and not chlorinated. "The Lincoln Memorial Reflecting Pool is not continuously chlorinated in the same way a standard swimming pool is. Instead, it relies on a large circulation and filtration system that draws water from the Tidal Basin and uses ozone disinfection."
"Yes, a 15 to 30-inch deep pool is highly likely to develop algae. In fact, these shallow depths are ideal for algae—which thrive in warm, sunlit, and stagnant water. Airborne spores land in the water and can multiply into a visible bloom within just 24 to 48 hours."
The water in the Tidal Basin comes directly from the Potomac River. "The Potomac River supports several types of algae, including essential green algae and diatoms, but it frequently experiences blooms of cyanobacteria (blue-green algae)." Source of quoted text: Gemini
* "A Petri dish is a shallow, transparent, lidded dish used by biologists to culture microorganisms like bacteria, fungi, and cells. It is usually filled with a nutrient-rich gel called agar..." Source: Gemini
Despite a multimillion dollar renovation project which saw President Donald Trump ordering workers to paint the base of the National Mall's Reflecting Pool blue, algae could be seen in the water, turning the water green