green water is excess nutrients in the water column that has caused an algae bloom, It's farily common to see and just takes some water changes and something that will take the nutrients out of the water column, plants that float do a good job at that.
Then I saw it. I saw a mom who would die for her son. A man who would kill for his wife. A boy, angry and alone. Laid out in front of him, the bad path. I saw it. And the path was a circle. Round and round. So I changed it.
-Joe (Looper 2012)