Ooh ooh I have done this. Well sort of.
No need to use a glass aquarium (might it crack if you have deep freeze - thaw cycles where you live?)
Anyway, I made a mini-pond that did great for 6-7 years out of the largest Rubbermaid container I could find. Maybe 55 gallons? I had a few plants and goldfish in there; each winter I brought the fish inside so they wouldn't freeze to death.
Fish were necessary to eat the mosquito egg rafts as they were laid, as skeeters can be bad here in summer and they breed profusely in standing water. I just bought cheap feeder fish.
With the plants to provide shade and oxygen it was a balanced little self-sustained ecosystem. I have since built a larger "real" pond and still have an original goldfish from the old one, he is I guess about nine years old now.
I cleaned it out each spring, but the water does need to be aged and/or conditioned before putting fish or plants in. Most municipal water is treated with chlorine and/or chloramine, which will kill plants. Also the rubber/plastic containers may outgas some funky stuff, so I suggest letting the water sit for a week or two, then sit again after refilling, before putting any live stuff in. Feeder goldfish are voracious eaters and poopers
so great for getting a pond or tank populated with good bacteria. They are extremely cheap and the poor things have a high mortality rate, as they are kept in horrid conditions and fed as food for larger fish. So I figure they got some freedom and fun after I bought them, most died, and the survivors were pretty tough.
Otherwise it was absolutely zero maintenance. I attracted dragonflies and frogs and various bugs, even in the little "Rubbermaid pondlet".
The goldfish kept the algae down. I now have a 8x4' pond, with a deep well at one end below the frost line, so the fish and frogs make it through our rather brutal Michigan winters. They just burrow into the leaf debris at the bottom and hibernate.
No bubblers, filters, nothing. Enough plants in the water will keep everything balanced and clean and encourage a healthy bacteria load.
tl;dr version: Tiny ponds can work. And don't let anyone tell you that a filtration system is necessary because it isn't.
