Fish, especially Betta, do not do well in bowls. Unfortunately, Betta fish are put into containers much to small for them to be happy or healthy. Many "Betta Bowls" are horrible at keeping fish. Bettas need a MINIMUM of 3 gallons (11.4 L) of water (5- 10 is ideal but the more space the better in most cases) with adjustable heating, and filtration. If you set up an aquarium that meets these requirements you will have a happy and healthy fish.
Feb 5, 2016 - Betta fish are often housed in bowls
The filter uses a pump to draw water out of the aquarium and pull it through a system typically composed of mesh, aquarium floss and activated charcoal, although the exact materials vary between types of filters. The filter cleanses the water of pollutants that harm goldfish, including excrement, plant and food detritus, chlorine, nitrates and heavy metals. It encourages beneficial bacteria to consume organic waste by trapping it in the filter medium. Without a filter, these contaminants remain in the water and reduce the amount of oxygen available to your goldfish, making him prone to bacterial and fungal infections. Two basic types of filters are available: in-tank and exterior. Both are suitable for goldfish. In-tank filters that submerge work best for bowls and small tanks that have no room to hang a filter on the exterior. Exterior filters attach to the outside of a tank or inside a cabinet and pull water out of the tank, cycle it through the filtering mediums and return it to the tank.
That means no filter, and no heater
Fish bowls are not the best housing for most animals. They're usually far too small, ranging from 1 pint to 2 gallons. There's not enough volume for your animal's water, plus gravel, plus decorations. Bowls without gravel breed harmful bacteria, and many aquatic animals with nowhere to hide can literally die of stress. Bowls also encourage stagnant water by having very little water-to-air surface area and no room for a filter.
sorry the can was pointing up a little to much, but you get the idea.