Fighting: Bettas are naturally territorial and will defend their territory against any perceived threat, including another Betta. When a male and female Betta are placed together, they may engage in fights, chasing, nipping, and flaring their fins in an attempt to intimidate each other.
Stress: Constant conflict and high level of stress from living in shared territory can compromise their immune systems, making them more susceptible to diseases and potentially shorten their lifespan.
To ensure the well-being and safety of your Bettas, it is generally best to keep male and female Bettas in separate tanks or provide a well divided tank with physical barriers that fully section off their area to prevent a direct sight lines and encounters