I decided to move Sal, my newest male, into a 10g tank. I have one already set up on my fireplace hearth so I moved it over a little & set up the new one right next to it. Got everything put together, acclimated Sal & then released him into it & as I thought he & Simon saw each other & boy oh boy was there some big flaring going on as I expected there would be. So I cut a piece of cardboard & put it in between & now they're both happy campers. Sal is exploring the entire tank & stretching his fins! I love a happy Betta.