If order for you to care for your Bettas so they have the best health possible you will need to give them conditions as close to their natural habitat as possible. The tank will need to be of the right size, not to large or small:
When Bettas are about 11/2 to 2 months old they will begin to fight with each other. It will be necessary to separate them one to a tank about this age
The tank should not be smaller than a half gallon (about 2 liters) but at least a gallon is preferable ...
 
 

 

The most imporant thing is that you have clean water, free from chlorine. It should have a pH of about 6.5-7.5. The water should be at least 7 inches deep. The water should be changed every 7 days. You should siphon the refuse off the bottom every two days. If you do not pay close attention to this the fish will become more prone to bacteria infections.
If you place the female in a smaller container (but not too small!) in the males tank it will help to improve the health of the male. He will show off to the female and it will keep him happy!
If you place the male next to another male about 10 minutes a day this will also keep him healthy and in strong condition.
The betta will prefer live foods but there is always a danger of infection or parasites. Adult brine shrimp works well but will need to be put in fresh water for about 10 minutes before feeding to reduce the salinity of the shrimp. Mosquito larva is their natural food and is great! There are many other live foods available that will work well. We also use the dried foods that are available for bettas . Some bettas are finicky and may not want to eat dry food but after a few days they will usually give in. If you are preparing for breeding, live food is the best. If you use live food and the bettas does not eat it you will need to siphon it off immediately after it dies as it will cause the water to go bad very quickly.