Hooked on Fish
Fish Tycoon that is http://www.bigfishgames.com/downloads/fishtycoon/
Its a lot of fun and a screen saver too. 
Give it a try and lose track of time.
The idea is you breed fish. The goal is to find the 7 “magic fish”. I just like making a pretty fish tank on my monitor. You sell fish for money and buy more things for your fish tank. Spend money to research so you can keep your rarer fish alive or sell fish better.
It runs in real time so when I leave a school of baby fish over night and exit. I wake up and load up the program to find a school of adult fish swimming around.