Betta Fish Vases Kill Betta Fish
At some point in recent history, people noticed that betta fish don't die immediately if you put them in tiny containers. Some people decided to exploit this by keeping bettas in tiny containers, and more recently, the myth that a betta fish can live from the roots of a plant has sprung up, causing people to create 'betta vases' for fish.
Let me state these for what they are, torturous death chambers for betta fish. There are articles on sites that deal with the topic of making a betta vase, however you will note that the authors of these pieces usually admit that they do not keep fish. This is the internet, and unfortunately, bad advice is quite often proliferated wildly by people who have no experience or knowledge in the subject matters they are writing on, however this article has been written by a long time keeper and breeder of Siamese fighting fish and is designed to explain why betta fish cannot survive in vases, and why you should keep plants in vases, and fish in fish tanks.
First of all, betta fish are anabantoids (air breathing fish) and need access to the surface of the water to breathe. If you plug up a vase with a plant, they will drown.
Even if a betta does have access to the surface in one of these vases, it will quickly perish because it also needs clean, heater water. Ideally, a betta fish should have a heated, filtered 5 gallon tank. The very idea of keeping a beautiful fish in a tiny vase without changing or filtering its water is stupid cruelty. Ammonia from the fishes urine will quickly build up, causing painful burns and a slow death.
If you happen to live in an area where the ambient room temperature never drops below 24 degrees, then yes, you don't need to heat a tank. If you do almost daily water changes on a tank, and I do mean 100% water changes, then yes, you can get away without a filter. But people who think they can put bettas in vases are not going to be ripping the plant out every other day to entirely change the water, are they?
Thirdly, bettas need fish food. They cannot live on plant roots. Expecting a betta fish to live on plant roots is almost as stupid as expecting a child to live on grass and demonstrates about the same level of understanding of basic care.
To summarize, betta fish vases are only advocated by people who don't know anything about fish and care more about making money than the well being and health of fish. If you try to keep a betta in a vase, it will die and not only will you have given a beautiful animal a painful death, you will have wasted your money.