It really all depends on the temperament of the fish you get. These fish are not really in the "great compatibility" range but it can definitely be pulled off. Sometimes Bettas can get aggressive with guppies as they may see their flowing fins as competition. But once again it depends on the fish. When I was acclimating my Betta to a community, I put him in a breeder cage so the fish could get used to each other at a safe distance, and it lessened aggression. Now he lives happily with my bolivian ram and dwarf gourami.