I'm slightly in love with my new Pygmy cories

They look so teeny tiny in my tank! My
LFS only had four so I took them all home - the guy said they would be ok but would they be happier with more friends? They're in a 20G with one molly and about 15 molly fry (who have a forever home waiting as soon as they're big enough), any suggestions for good tankmates in the future?