Bosemani rainbows are lots of fun to watch. Very active, usually hovers around the mid-level of the tank, or at least when I had 3 of the Bosemani, that's what mine did. Hungry little hippos... mine were ALWAYS begging for food. 5 of them would make a really nice looking group. I'm not sure I would go with the tiger barbs myself, as they have a bad rep for being fin nippers. The zebra loaches are beautiful fish, and 5 of them along with 5 bosemani rainbows would be great for the bottom and mid levels of your tank.
If you wanted a larger school, yet wanted to stick with loaches, there are the Yasuhikotakia Sidthimunki. (common name: dwarf chain loach) They're not cheap... something like $14-20 each, and need to be kept in a group of at least 6, but a group of 10 would look fantastic. If money were not an issue, I think I might do 10 dwarf chain loaches, 5 bosemani rainbows, and 6 marbled hatchet fish. (that would be close to $300 worth of fish, assuming $20 each for the dwarf chain loaches) That might be a little on the high side as far as bioload is concerned, but should be easily manageable with a little bit of experience. Weekly 30-40% water changes would probably keep them plenty happy.
Those zebras really are tempting though, I almost bought several of them when I still worked at Petsmart. (they used to sell them, they changed the planogram and have since phased them out) I'm sure
www.liveaquaria.com would have them, though shipping will cost you a pretty penny.

How do you plan to aquascape the tank? Gravel, ornaments, and fake plants for simplicity? Or are you going for a more natural, live plants, sand, and driftwood approach? When I had clown loaches, they did like to nip at some of the plants, which drove me nuts on occasion, but they were so playful and fun to watch that I could never really stay upset with them.

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