tiger barbs/ tetras?

Question
Hi, sorry but I think this is going to be kind of a long question.

I set up a 30 litre freshwater tank, not sure what that is in gallons or whatever. I have 4 tiger barbs in it (2 regular, 2 green), which I got 3 days ago. How long should I wait before adding more fish? I have been researching tiger barbs compatability with other fish, some sites say they can be mixed with tetras and some say they can not. I would love some rummy nose or neons but dont want to put them in of they are going to be killed. I know tiger barbs are supposed to be less aggressive if in a large group, how many exactly would I need? Do they have to be tiger barbs or could I get any other kind of barbs?
This might be an insane thought (sorry if it is!) but my fish are constantly looking at their reflections in the sides of the aquarium and trying to fight them, would this make them think they are in a larger group than they really are?
please please I hope you can help!

Answer
Hi, tiger barbs should be in groups of about 4-5, they will go whell with almost any other fish, i have had 3 and they mixed with  almost anything i put, but make sure to buy large sized tetres, not less than half an inch, Just wate about 3 days before adding other fish once you have got your first 2-3.Good luck if you have any other questions i will be glad to answer them.THANKS!