If you want to house a Betta couple together the aquariums doesn’t have to be big and Bettas are know to successfully spawn in aquariums no larger than 5-10 gallons. The aquarium must contain a lot of good hiding spots because the female needs to hide from the male to relieve stress and avoid injury. Live plants will help you keep the water quality up, but artificial plants will be just a good as hiding spots.
The Breeding Couple
Chose a male and female fish of roughly the same size, but do not house them together yet. (They should be of roughly the same size to avoid one of them ending up badly injured.) The pair should be given a lot of nutritious food; you can for instance provide them with a combination of high-quality flake food and live brine shrimp. The water quality must also be kept up and the water chemistry should resemble that of their native environment.
When both fishes are healthy and well-fed, it is time to introduce them to each other. Start by placing their aquariums close to each other and allow them to watch each other for a couple of days. Proceed by making it impossible for the male to see the female for a while, before moving him to the breeding aquarium. When the male has spent an hour or so getting used to his new home you can put the female in a hurricane globe and gently place it in the breeding aquarium. This will prevent the male from getting at her right away. Carefully monitor your fish and see if they show any interest in each other. Flaring is a good sign, and hopefully the male will soon start building a bubble nest.
Do not release the female from the hurricane globe until the male has built a fairly big bubble nest and the female is showing vertical strips. She should also be assuming a head-standing position in the globe and ideal have a protruding breeding tube (look behind the pelvic fin).
When you release the female, it is perfectly natural for the couple to engage in some nipping and chasing. Keep an eye on them and only intervene if one or both is getting badly injured. Really violent attacks means that they couple is not ready to breed, or simply incompatible. Place the female back inside the hurricane bowl and let her stay for a few days.