Charming game!

Zen Koi is exactly what its name implies; a tranquil time-waster that is easy and soothing. Leveling up your fish is fairly easy when you learn how to catch each prey type. Pearls (the in-game currency) are fairly easy to come by, if you are patient. They are lots of different colors and patterns to the fish, and breeding for the ones you want can be a challenge.
If you just want a game to play while you are waiting for an appointment, or watching a dull TV show, this is the game for you. Easy, pretty, interactive.

SandyBratzel about Zen Koi Classic, v1.7.0