How large and/or heavily planted would a tank have to be to support two male bettas?

[The Fish]

I've heard that bettas in the wild will generally retreat instead of fighting another Betta and that got me wondering, How large and/or heavily planted would a fish tank need to be to support two or more bettas. I am asking this because I am curious and not because I am considering this for a setup.

[Daniel]

When I used to breed bettas, I could put 40 or 50 males in a 10 gallon aquarium because the crowding would overwhelm any sense of territoriality and there would be a bit of fin nipping but no fighting.

I would be reluctant to put 2 males in my 500 gallon tank, because if they were mature and healthy they would seek each other out to fight. It might not be fatal, as one would certainly retreat, but the victor would keep looking for him.

On the other hand I would not hesitate to put a dozen males in here.

[gardenman]

A lot would depend on the personality of the individual bettas. Some are pretty chill and could get along pretty well while others are hyper aggressive. Adding a bunch of female bettas might help quell aggression a bit also and could help keep the boys distracted. (Or it could lead to more fighting.)

[demicent]

Like you, I wouldn't do it personally.  The stress levels would be high.  Some people use opaque dividers in the tank.  Occasionally the fish will get around or over the barrier, not with good results.  

[Max G]

It just seems like a good reason to get two fishtanks!