Funny, I was sort of exploring the idea of aquaponics myself and I was trying to explain to someone what was at the root of my curiosity and I realized that it was enclosed ecosystems. I had fun giving the lettuce to people and explaining that it was grown without ever seeing natural sun or soil and showing them a timelapse video of the growth, but no one seemed all that impressed lol.

If you've never been, I can highly recommend a trip to "Biosphere 2" in Arizona which is a semi-retired monument to the whole idea, and quite worth the tour.