The  Siamese fighting fish is one of the most popular species of tropical  aquarium fish. For centuries these fish have been captivated by people  for hobby and sport. In Thailand, breeding these fish has become a way  of life, and is the focus of many gambling events. These fish are known  mainly for their aggresiveness, mainly that towards their own species.  Male bettas are extremely territorial, and will kill each other when  encountered.
This fish is also the subject of much controversy.  Since it is a labyrinth fish it doesnt require much oxygen in its water  and can breathe air directly from the surface, its also very slow moving  and often prefers to swim in one spot. Because of this it is possible  to keep these fish in very small bowls and tanks, some are sold in bowls  that are similar to large shot glasses. Many experts view this as cruel  and say that no fish should be kept in less than 1 gallon of water,  especially since bettas are used to large rice patties in the wild. I  myself agree and would like to add that I think the minimum requirements  for this fish should be 5 gallons with a filter. I personally believe  you will NEVER fully appreciate a betta until you see how healthy,  happy, and colorful they are in a proper aquarium.
Bettas are  also a tough breed offish to establish in a community. Its agressive  behavior can be destructive to some fish, meanwhile its own long fins  could prove to be a snack for nippy fish like barbs. Male bettas are  extremely territorial and will kill each other on sight. This is how the  fish earned their name and betta fighting has become a gambling sport  in many places. This is also controversial and is considered by most  aquarists, including myself, to be cruel.
In the wild, the  fighting fish's diet consists almost solely on live insects. They can be  fed regular tropical flake food but must be supplemented with freeze  dried bloodworms and occasionly live foods. However the ideal diet for  the betta is live and meaty foods. Brine shrimp, Daphnia, plankton,  tubifex, glassworms, and beef heart, are good diet options.
The  male fighting fish is easily identified by its long and colorful fins.  Females however are much duller in color and have significantly shorter  fins. Dozens of selectively bred variations of the betta splendens are  available including the regular veil tail, the crowntail, the half moon,  and the double tail.
Breeding the fighting fish is considered  extremely difficult. Males should only be bred with one female at a time  and can also be very agressive and hurt the female while breeding. The  water temperature should be raised to 30C and should be filtered by a  smaller filter to prevent excess water movement. Before breeding the  male will construct his bubblenest to place the eggs in, after he will  begin chasing the female agressively, which may result in her loosing  some scales. Once ready the two will show bright coloration and the mall  will wrap himself around the female. Eggs will be fertilized  immediately, and after mating, will be placed in the bubblenest and  cared for by the male. The female should then be removed as the male  will once again become violent. In about 2 days the eggs should hatch  and be visable in the nests. For the first 36 hours the fry will feed  off their yolksacks and continue to be raised by the male. After 2 days  the fry should be free swimming and the male removed to prevent him from  eating the fry. They should be then fed a diet of baby brine shrimp and  other tiny fry food. Bettas are so agressive they need to be seperated  at an early age, providing isolated housing for each fry becomes tedious  work and often requires the use of a large barracks system, limiting  the breeding of this fish for professional breeders and less for the  average hobbyist.
Credit to ekanlaga.blogspot.com