If you have more than one fish, buy a divided betta tank or separate bowls, the bigger the better.
Give them a betta blend, only what they will eat in a few minutes, once or twice a day.
Replace up to half the water once or twice a week, leaving fish in bowl. Add conditioner to neutralize the chorine in most public water. Avoid winter drafts; 80-degree water is ideal.
Choose active fish with vivid colors and no tears or sores. A bubble-nest shows that a male is young and industrious.