I guess it depends on the betta. I had one (an otto) in my community with a betta....my betta hate,hate,HATED the otto, I don't know why,poor little guy minded his own business and worked all the time,but one day the otto just disappeared
I guess just go for it....have something/place on hand in case it doesn't work out, but it should be ok ,my oldest betta is just a mad psycho killer ,yours may be very hospitable to his new tank mate
I have 3 otos in with one of my male bettas in a 5.5 gallon tank. He likes to pretend he's a tough guy sometimes and he flares at them, but they're all okie dokey in there.
i yanked him out all right....i dropped in my otto without my betta noticing. he strolled over, eyed him a split second, and *gulp*....took a big bite. i yanked my otto outta there so fast it made my betta's head spin. as of right now, my otto's not harmed in any way...just a bit frazzled.