The males will also cause injury to females in their drive to reproduce. Female betas are not aggressive, and can be housed communally. No one should ever buy multiple males with the intention of using them for the morbid entertainment of allowing them to combat. This is inhumane and inexcusable treatment of a living creature. Housing two male betas side by side in separate quarters will deliver greater pleasure, as the two fish display and threaten with no injury to one another.
Betas originate from the slow moving, slightly stagnant waterways and rice fields of Southeast Asia.
For this reason, Siamese Fighting Fish do not require the same aeration and filtration systems of most aquariums. They can live quite happily in a variety of habitats. However, just because the beta can survive in a cramped, stagnant bowl with no plants or gravel, that doesn't mean that they should be sentenced to such a life. The tiny bowls or plastic punch glasses in which these fish are sold are not suitable for long term habitation. Find a reasonably sized aquarium, goldfish bowl, or even a huge brandy snifter, and add some gravel, a live or plastic plant, and some interesting accessories.