At the time of writing, the Rio 2016 Olympic Games are still in full swing. The diving pool which had turned a nasty cloudy shade of green is apparently fresh and blue once more. But, the tale of how it turned is tortuous. Any observer with outdoor pool experience saw the telltale signs of an algal bloom, the hue, the cloudiness. Indeed, the organizers declared algae were to blame after deferring an announcement for several worrying days. However, they stroked backwards on that claim and blamed alkalinity. Then there was an announcement that it was the inadvertent addition of hydrogen peroxide. Pundits suggested an excess of algaecidal copper sulfate was to blame, but copper sulfate solution is bright deep blue and copper chloride solutions are pale blue. Other pundits put it down to various difference chemicals, such as fake tan, skin moisturizer and even an additive to reveal when someone urinates in the water! But whatever was claimed and whatever the cause chemical or environmental, the pool had bloomed with algae. Life will out and chemicals were the remedy.