Be careful when u buy fish they can be sick sometimes and depending on the breed of fish u can't put something's together unless u want dead fish..... Like my sisters betta got killed by a guppy as bully's r known to bite at long finned fish
That's weird, it's usually the other way around, Bettas kill Guppies because they think they are other male guppies. I had a tank a while ago and got a betta with my guppies and never got a single issue.