Keeping males together?

[Kithy]

Definitely set it up on a day or two where you can watch them closely with an emergency tank set up just in case.

[jsgossamer]

There have been actual studies on Bettas and habituation. They proved that Bettas constantly exposed to seeing each other will lose their aggressiveness towards each other. That doesnt mean they can live together, it just means that if you have them next to each other they will eventually ignore each other. I have two split tanks, and two tanks at work where the bettas are directly next to each other. The only time they actually pay attention to each other is a little extra excitement at feeding time. I actually havent seen my bettas flare in a very long time.