Self-sustaining aquarium in a jar? I've seen some videos of people scooping up some water from a natural body of it, adding some sand and a few plants, and soon enough, they have a (near) self-sustaining aquarium. I've always wanted to do this, but I'm not exactly sure how. There's a river in a small ravine (about 20 ft. deep) behind my house, and a nearby pond, so I think I might be able to manage this, but before I do, is there anything I need to know, or any suggestions on how to pull this off? Thanks in advance!
P.S. I don't want to take any animals (such as frogs), and trap them is a confined space. All I really want is some organisms that are just large enough to see, and I think I'd be good. If I do take anything from the wild, though, I want to return it, and I want to make it a pretty darn good habitat, so it doesn't feel trapped.
It is called an aquarium, put what ever you want in it. With natural waters you have a good chance of collecting dragonfly larva , which will eat about anything else you catch including small fish. Chances of mosquito larva are low in my experience. I don't know why you would not want frog or toad tadpoles ; I have a couple very small feral ponds in my yard and various frogs and toads  deposit uncountable numbers of eggs &gt; tadpoles. Some years I have taken thousands of tadpoles to nearby lakes and dumped them . When I don't do that most get eaten by siblings. You are unlikely to find suitable native plants other than duckweed, so I suggest buying Hornwort at a pet shop -pretty bullet proof.