I suggest you try this link for info on the most popular Molly, the Black Molly
http://www.bbayaquariums.com/black-molly.html and then get a copy of a book called "Mollies: Keeping & Breeding Them in Captivity". It is a very good book. Another good book for live bearing fish is called "Guppies, Mollies and Platties A Complete Pet Owner's Manual".