The last page of the Dresden Codex is thought to refer to the destruction of the Earth by flooding and what appears to be black rain. Since the Codex encompasses advanced astronomical data and predictions, it's curious that no date was ascribed to the armageddon event depicted.
http://www.thecityedition.com/Pages/Archive/2010/Mayan_calendar_Page3.html
Just to let others know...
A typical ionic footbath is pre-set to a 30 minutes treatment. So, you'd have to do 2 at a time. I've done that 1 hour treatment many times and after the 2nd 30-minutes round the water is a lot darker, although it depends on how old the array is.