Hit or Miss I acclimate the in a Container then dump them in lol, Alot depends on the betta my current male in my 75 community tank does well doesn't mind anything even the fancy guppy males. He does eat the guppy fry but not great loss since I am not trying to breed them they just do that constantly. My Prior female i had to remove as she Pretty much wouldn't tolerate anything else that came within 6 inches of her. She is isolated now ina 5 gallon tank with some wild Type RCS that annoy her to no end. I mean she flares at her food, she flares at the shrimp, she flares at me, and she attacked my hand the other day when I was cleaning her tiny domain.
All in all take a few hours to watch when you first put the betta in, in a big enough tank the Betta will stake out a small little domain with low water flow and pretty much hang there although I find mine all over the tank at various times a day, he goes back to the same spot to sleep after the lights go out.