Originally Posted by Dianacatz
When I was Young my dad kept a tropical community tank with a betta. A lot of cardinals were kept in the tank with the bettas and they got on fine.
Cardinals? There are several different species of Cardinal fish. I assume that you mean the smaller species that only reaches two inches in length. Bettas can be kept with other community fish, but males will fight. Male Bettas will nip guppy's tails until they succumb from infection. Definitely not a great idea to keep guppies and Bettas in the same tank. Guppies, especially males, have long, inviting tails, while bettas are fast and see these tails as aggressors. I've successfully kept my female crowntail betta with my gups, but my male took chunks out of one of them.