It's known among betta keepers not to put guppys with Bettas. When you read somewheres it is ok, that doesn't mean it really is. There will be more sites saying not to. The fins make the guppy look like a betta. Even if guppys are fin nippers, matching chewing abilities with a betta is not wise. Bettas can get along with almost any fish that will get along with it. That doesn't mean it will get along. They pretty much do as they please unless there is something more capable of chewing in with them. A good example of not always believing what you read, is this message board, and every other board. Everyone has an opinion. Some are right, and some are not. Sometimes they both are right..lol