Everywhere I look I see information saying that you should keep your Betta in a tiny fish bowl or glass.     I always read everything that I can about animals that I like......even fish.    This is going to be a very short guide because all that I wanted to say was that BETTAS SHOULD BE KEPT IN A 10 GALLON TANK......AT LEAST!    They are able to survive in a small space but just because it can survive is no reason to deprive it of a better life.    So, if you have a Betta that you have living in a tiny water vessel, do the right thing and move your fish to a 10 gallon aquarium.    He can live with other fish, just not a Betta of the same sex.    Also you will get to decorate your tank with hollow logs or castle or whatever to allow your fish to live a haapy life.....not just be a captive in a 12 oz bowl!

Good Luck!  And Happy Fishing!