Females are generally okay together. Males should not go together. They are called Siamese Fighting Fish for good reason. Some males can be put with females but not always, and sometimes they can go together for awhile but then things turn and get ugly.
There has only been one instance where I have mentioned putting 2 males together and they had been together in the pet store for a long time before coming to their new home. They actually suffered some loneliness when they were seperated. BUT in all other instances there is no way 2 males or a male and female should be housed in the same tank!! If you plan to have females in the same tank, I can tell you from personal experience, believe me, do not buy them at different times and if possible get them from the same place. They can be as aggressive as the males to females they are not used to. I would never put a male/female combo into a tank at any time unless you are planning to go into professional breeding and have their set-up in a special tank just for breeding and have READ, READ, READ on the subject and properly prepared.
no not fin types their are called Crecent bettas the only thing difrent about them is that the malles don't fight each other. this is only what I have read in only one book so I can't be sure ill start a topic about them soon
There is the Betta smaragdina or Peaceful Betta, who do not attack each other unless competing for the attention of a female. They are being more commonly sold now and some of the books are beginning to say that they may someday replace the Betta splendens as the most commonly sold Betta.
The Betta splendens is the Betta that I am sure most of us have here and is divided into the various fin types of: Veiltail, Halfmoon, Crowntail, Delta, Superdelta, Doubletail, Combtail, and other fin types. There are many more species of betta that you will never see for sale or in any fish exhibit simply because they are rare or exist only in the wild. There are others that do not lend themselves to aquarium life and are not attractive so would not be commonly desirable. There are others that are bred especially for fighting which is why the Betta began to be kept by humans after all.