A betta should not be confined to a teeny tiny container because:
1. Nowhere to swim or hide
2. The water becomes a mess faster
3. It is hard to clean.
You should not put males in a community aquarium because:
1. Long fins prove to be a temptation for fin-nipping fish.
2. Long fins also tempt bettas.
3. A filter for a community is too strong for a betta, which requires gentle water.
A betta should live in minimum one gallon of water. A good rule to remember: The smaller the living quarters the more frequent the water changes.