Not to mention the fact that if those guppies are fancy tail guppies, they won't be fancy for long with the tiger barbs. Also, I have seen fish that don't ordinarily nip fins go after my betta like you wouldn't believe. My killifish had never bothered any of my other fish. I put in a betta to see if it would work and they went to work chewing on him right away. So if fish that don't ordinarily nip go after a betta, you could expect a known nipping fish to go crazy! Tiger barbs would be devastating on your betta no matter how many you put in, and probably wouldn't be good with the guppies either.
38 Gallon (Freshwater): 1 Green Swordtail, 3 Yo-Yo Loaches, 1 Clown Pleco, 1 Blue Gourami, 4 Otocinclus, 7 Cherry Barbs.
46 Gallon (Saltwater): 60 pounds Lalo Live Rock, 60 pounds aragonite sand, 1 Coral Beauty Angelfish, 1 Peppermint Shrimp, 1 Mushroom Coral, 1 Emerald Crab, various snails and hermit crabs.
10 Gallon (Saltwater quarantine):