Eco-spheres are glass, self-contained ecosystems that can last up to 15 years. Shrimp, algae, and bacteria sustain each other with no need for care except providing indirect sunlight.
Eco-spheres were originally created by NASA when studying the possibilities of closed ecosystems for humans.
Eco-spheres range from $80 - $500. (The smallest are currently on sale for $63)
(Source: honestlycassie)