The saving grace to all this is that by nature, Bettas use very small areas to claim as "their territory". Once they get past this stage and can be out of sight of the other fish, you may have a chance. They fight for territory and that's just about it.
No offense intended on my previous comment about your research but you have to admit, being surprised that your Siamese Fighting Fish didn't get along really sounds like not enough research was done. Having them NOT fight is more of a shock quite frankly.
The internet is an amazing place full of info and MISINFORMATION so you need to take all that into consideration. Even this forum has more opinions than facts (IMO
) regarding Bettas. The variety of tail doesn't change that they are all Betta splendens. They all have the ability to fight. If you look up the wild fish's behavior, then look up the origination of the domestication of this fish, you'll better understand the points I was bringing out.
Hopefully, it will all settle down for you but you can't be surprised if you come home one day and find only 1 live Betta in that tank. That's the chance you are taking by mixing more then 1 Betta in a tank.
I sell my Bettas in a friend's Pet Shop and have watched my females beat the snot out of the existing females in the sales tank within the first 5 minutes of being in there. I've had shippers sedate the females so they don;t beat each other up on the trip over from Asia. They are just NOT designed to be kept together. BUT, sometimes, the fish don;t read their owner's manual and do crazy stuff. Maybe you will get lucky
Keep us posted