breeding and being able to tell males from females

Question
i have 2 mollies in my fish tank. one is a white molly and the other is a dalmation molly. i cant tell if they are a boy or a girl, the dalmation follows the white one around but there was a mysterious bump on its belly that formed, so we put it in our breeder but after a while, the bump was either smaller or it was gone?? so we took it back out of the breeder, should we have done that? why did this happen and how can you tell the diference between boys and girls??

Answer
Hi Braden;

The key to sexing mollies is in their bottom rear fin, called the "anal fin". Female mollies' anal fin is fanned out. In males it is pointed. Below is a link to photos of male and female platies, cousins to mollies and sexed the same way. The male is on the left in the photos. Look at the fin between the tail and the two bottom fins on the belly.

http://fish.orbust.net/livebearers.html

It is easier on your female mollies to have at least two females per male. Males are interested in breeding constantly and can chase a female enough that it stresses her to death. Provide plenty of hiding places for the females so they can rest occasionally. They really like live plants, bushy ones. If you miss the delivery of babies, they can hide in the plants too.

Mollies can have babies about every 6 to 8 weeks. You will know when the female is close to delivery when her belly gets very large and gets a bit flat on the bottom and sides looking a bit "boxy". She will also hide more a few days before delivery.

At Your Service;
Chris Robbins