Black Magic is just that, full of magic.  Ok, not really but the leaves do change from green to a dark black/purple color with the more sun exposer they get.  This is a clumping ee.  Meaning it doesn't shoot off runners like some ee's but rather produces baby plants right next to the mother.

 

This colocasia does very well in water during the growing season.  I would not recommend leaving it in the water year round.  Come winter I would expect the tuber to turn to mush.