Often they get more aggressive when the water parameters are off. If you have a recent tank set up, it is likely the tank is starting cycling.
Do you know what the Ammonia, Nitrite and Nitrate?
Probably if you don't have a test kit, do a couple 40 to 50% pwc
's (partial water changes)
Also Barbs will often be really active and seem to act aggressive and can be bullies. People say they have nice calm ones but often that is not the case. They also prefer larger groups of their own kind 1 male to 2 or more females.
I just learned about cycling but I already have fish. What now?! - Aquarium Advice
Fish-in Cycling: Step over into the dark side - Aquarium Advice
This is a good thread for learning all the basics.
Guide to Starting a Freshwater Aquarium - Aquarium Advice