I think this is what you were looking for based on you saying they have little shrimp like creatures inside: Eco-Sphere
Yo guys, my girl's bday is coming up too. I wanted to get her one of those glass spheres with the self sustaining ecosystem in it. I totally forgot what they are called. Does anyone know? They have little shrimp like animals living inside. Incredible stuff.
Here is the About section that shows the little shrimp like creatures.