I am a tiger barb lover, those are by far my favorite fish...
They are active, not shy at all, semi-agressive, schooling fish, so the *minimum* I would recommend is 6. Plus, they make a wonderful display together. Very, very easy to care for.
Since they are semi-agressive, and **based on your tank size**, I would do a species tank, that is, only tiger barbs. I would take in ONLY 6-8 of them (because they grow REALLY fast).
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I just saw the previous post, saying you may get away with 4. I really woudn't do that though, cause I tried before and all I got were 4 scared barbs hidding behind the filter). The rule for 1in of fish per 1gal of water is somewhat open to debate but I don't think there would be a problem with 8 barbs in a 10gal because they are tight schoolers)... In fish, pretty much a lot is debatable...
LOL
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Your tank may look a little empty but, believe me, once they get growing it wont. Don't get more than that unless you are planning on expanding to a larger tank later...
Also, it is good to give them plenty of room for swimming around, they are fast swimmers!
To get over the feeling of empty tank, throw in some wide-leaf plants (like the amazon sword) and maybe a small piece of driftwood... They like to "sleep" about the leaves. When they "sleep" they do a "nose stand", so cute...
Here goes the data:
Max size: 3 inches
Water parameters: pH slightly acidic, about 6.8
(but they aren't that picky about that, so as long it is within the 6.5 to 7.5 they will be fine.)
What they eat: anything, ranging from cucumber to pelets.
Temperature: 75-80F
Oh, good fish choice!
While you wait to get the fish, get the water started if you didn't yet.