While that bit of history might paint a brutal picture, the modern female live betta fish has a more community-minded temperament and will generally share a tank with other female bettas and non-aggressive fish. Male betta fish are another story, however. While they can also live successfully in community tanks, a male should never be placed in an aquarium with another betta (male or female), as it will reawaken that old fighting spirit. Two or more live betta fish in one tank will become aggressive and combat each other – often to the death – to determine which betta is the alpha. Pet parents who want to pick up multiple betta fish for sale are strongly urged to keep them in separate tanks.
I lost a fish yesterday at clamped fins. In the store they said (since i never saw this happen to my betta’s before) it was finrot. So i treated him against it. Yesterday evening, he suddenly died. Today i noticed my black male crowntail now has it to (they were sitting totally apart) He is still eating and coming regulary up to breath. I added a picture:
Young Halfmoon Male Betta Fish Picture - Pinterest
Siamese Fighting Fish Stock Photos and Pictures | Getty Images
Due to selective breeding there has been some evolution to the betta fish, no longer a dull green / brown, betta fish are now known for their bright colors and big flowing fins – like that of the halfmoon betta (see some Japanese fighting fish pictures below). Sadly these fish were also bred to fight. Similar to cock fights, betta fish were bred so that gambling could be done over the victor of a betta fight. This has led to an increase in aggression and fight length for domesticated betta fish, meaning it is important to and to never put two male bettas together.