Well, cycling the tank with fish is not recommended but that will not really help you now. Just keep up with the water changes. Every day or two until the cycle is complete. And since it's only a 5 gallon, go ahead and do 50% each time as it's not really any more work to do so. Also, get yourself some "prime", made by seachem. Arguably the best water conditioner on the market. It also detoxifies ammonia and nitrite so double up on the suggested dosage to both condition and detoxify. If you use a baby medicine syringe to dose, a bottle will last you a really long time.
Me, I love tigerbarbs. But they do tend to be a little nippy with both themselves and other types of fish. If you add other fish to the tank, make sure they are fast swimmers.
Good luck with the tanks and welcome to the forum.