^^ agreed.
this is an extract from my website, it is the quick version, bhut you will need to research loads:
The decision of breeding bettas should not be taken lightly, it requires extensive research and much thought, time and money.
2 of the healthiest bettas should be used. Each betta will require conditioning; this is basically feeding them lots of live foods.
A spawning tank should be set up (5g-10g) with a heater set at 29C,and a sponge filter. The female should be put into a chimney until the male has built a bubble nest, after 2 days the female can be released.
After spawning takes place, remove the female immediately, the male might kill her if he feels threatened. 3 days later fry should be free swimming, it is now time to remove the male or he will eat them.
Whilst taking care of the fry, it is also important to check on the health of the parents, carry on feeding them live foods for 2 days or so before weaning them back onto dry food.
Feed the fry 3 times a day with high protein live food, micro worms, vinegar eels, baby Brine Shrimp are all excellent.
For the first 2 weeks tank should not be cleaned, but after this switch on the sponge filter and do daily water changes of around 50%. The fry will dramatically grow with water changes.
At around 6 weeks, start feeding fry dry food, along with the live cultures. By this time they will have developed their labyrinth organs. It’s now also the time to separate all the males into individual containers as they will start being aggressive. These containers should be 1l minimum, and daily water changes will need to be done. As there is no heater for these, they will need to be kept in a warm room.
At around 16 weeks they can be sold on.