Ecospheres were first invented 13 years ago, but they're awesome, they're now affordable and it's almost Christmas. If you haven't heard of an ecosphere, it is a small totally enclosed ecosystem which sustains the life of small shrimp and algae with nothing but daylight. The original designs were developed by scientists at NASA's Jet Propulsion Laboratory. The spheres have a life expectancy of two years, but some have been known to last for seven years. The Ecosphere site describes: "Inside each EcoSphere are active micro-organisms, bright red shrimp and algae, each existing in a clear "soup" of filtered sea water. Because the ecosphere is a self-sustaining ecosystem, you never have to feed the life within. Simply provide your EcoSphere with a source of indirect natural or artificial light and enjoy this aesthetic blend of art and science, beauty and balance."
The eco-sphere website will link you to giant ecospheres up to 39". You can also buy them at a number of different stores, including Hammacher Schlemmer.