Can I add a male betta to my tank with guppies?

Bettas will go after the guppies because they have frilly fins, almost like a betta. Only if you want to see dead fish should you do that. I wouldn't advise it. But there is always a tiny chance it will work. I had my betta in a goldfish tank with no problem. If you do try, keep a close eye out and separate them at any sign of aggression.