Keeping a Japanese fish bowl, vase or similar

There used to be (still is?) a Japanese shop in Leeds that sold highly aesthetic glass ornaments with very small fish in them. They used some kind of weed to create a living ecosystem, so there was no artificial aeration etc. Does anyone know anything about these kind of aquariums and how to set up and maintain one?

You are most likely thinking of some variation on the betta vase death trap. (Betta Splendens are from Thailand.) Bettas are beautiful hardy fish which can breath air from the surface of the water. This leads people to do various things like put them in small containers with a plant and not change the water. Anyone who claims they can sell you a self maintaining ecosystem for a fish is lying, or mistaken. (Well a pond can easily sustain about one fish per 100 gallon given a well established ecosystem.) A betta can live in an ornamental vase or other container if it's fed, and it get regular water changes.

The problem is most betta novelty contains these will not work for more than about 3 weeks. A healthy betta often can survive for about 3 weeks without food. (Note that more than a week of fasting will likely shave years off the betta's short 3-5 year life span.) In fact the lack of food actually helps prevent the fish from dying of ammonia poisoning. (Fish +food = ammonia) The plant is just a joke. Bettas are carnivores. Plus any 1st year bio major will note that you need at plants massing 10-20 times the weight of an animal to process it's waste, and provide food, and oxygen.