I think you could do less than 7, but don't get any less than 5. My LFS
has told me that 5 is the bare minimum recommended. Also, I have heard from all LFS
in my area that tiger barbs and tetras don't get along period. You might be able to try it if you keep a close eye on them, but I haven't heard good things about that combo.
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):