tenohfive
Always room for one more tank...
b*****d fish shops.
Thats the spirit! Welcome to my world, where fish shops lie or are wrong!
Don't take it personally mate, just spend some time on here and check out the species index for info on potential fish sizes - and when in doubt, ask on here. People will always try to help you out, and you'll quickly spot the people who give good advice consistantly.
I'd hang fire and let the tank mature. If you get stuck you can usually return fish to your LFS (local fish shop) - they might not give you a refund but if its an inexpensive fish thats not the end of the world.
The reason I mention BTS is because if you do your research you'll see fish that look spectacular - and you'll want them, but realise you need a bigger tank for them more often than not. There are some exceptions mind.