We built a Terrestrial Shrimp Support Module, or a jar with some shrimp and a few snails in it, according to this project idea in Make magazine. The main idea is that if you include just the right set of plants, animals and so on, they will be self-sustaining for a long time. That’s supposed to be up to 3 months but we’ll see.
It was fun collecting the stuff at the local aquarium store and the pond up behind our house. The boy here loves watching his new friends swim and crawl around inside. We are hoping they will last in there a while but we’ll see. If they don’t, that’ll just give us an excuse to go make another one.