Ive actually created a mini biosphere kinda thing in one of my bio classes. It was a large glass jar, 1 earthworm, grass, flower, and 1 plant eating beetle and then it was sealed with plasticwrap. The bottom was gravel covered by soil from outside. The entire setup was taken down in a month, all my critters were still alive. I wondered back then if it would work for the long run but i guess it wouldn't. its a very basic experiment, for some reason done at a college level. Guess my school doesnt have enough budget to do an actual experiment.
I have looked at bisphere 2. It is a very interesting experiement. The system was inbalanced, i beleive, and thats what mainly caused their failure. There wasnt enough light penetration, co2 levels fluctuated too much, caused booms in certain populations, resulting in lower oxygen levels, etc.
The idea i proposed would not be sealed off, ie set amount of oxygen and co2 so taht already is a big dent in the biosphere aspect, or aquasphere. I guess that alone would already create a huge variable for an experiment.
I still wanna try this to a degree, if it doesnt work, i can just switch to a "minimal human interference" tank. Does anyone have fish and plant suggestions that could work in tandem for a balance? ie, a type of fish/shrimp and plant that they are known to consume regualrly for sustinence?
Also, would the introduction of snails help? They do consume rotting food and pass them on as waste thats more readily decomposed by bacteria.