I've bought my first new tank and got some fish after about a month. I have bought four tiger barbs and only one of them is green and the others are stripey, the green barb has been bullying the others what should I do?!?!?!
You might well find that 4 Tiger Barbs is not enough to spread out their natural "aggression". I normally advocate having at least 6, ideally more - but your tank would be starting to look a bit overstocked. They might settle down, but keep a close watch on them.