I have hengeli rasboras (with one lone espi rasbora in the group) and they hang very tight together. I have 9 in a 10 gallon with cherry shrimp. Heavily planted tank. It's a lovely set up and nice to watch!
Here's a vid of my harlequins...not great quality but it will give you an idea...there are 6 in a 10 gal...
http://img531.imageshack.us/my.php?image=dscn29163750385fd9.flv