What tropical fish for new aquarium?

It's too small for Balas I'm afraid, these are way too big and active, they need a set up like this:

http://www.youtube.com/watch?v=gfbspqOI2sw&feature...

You could fit a shoal of 8-10 Tiger Barbs in there, just bare in mind these can be fairly nasty fish, in larger groups they should keep this amongst themselves BUT it would still mean you could pretty much only fit bottom dwellers in the tank after the Tigers, and any tank mates may still be nipped at dinner time. There are more "peaceful" Barbs out there, the Five-Banded Barb (Puntius pentazona) is a better alternative to Tigers.

Be sure to get your tank through the nitrogen cycle BEFORE you buy any fish! So you got a good few weeks of planning anyway.

Knowing 180 L is a 48 gallon tank, you could fit 15- 20 barbs, or like 2-6 bala sharks. Bala sharks get really big, so take notice to that

I don't know what kind of tank that is but I think mollies look like little black whales.Why not angel fish.