If you place a male and female (for god sake dont mix 2 males!) in a tank and you see the male spread his fins to the max then he is ready to mate. The thing is....you might need to go through many different females, if they start fighting take the female out immidiatley and place her in another tank. You can have more then one female betta fish in the same take just so long as it is not over crowding. I hope that helps you out!
