Molly Knocked-up??

[guns286]

OK, here's my problem. As I've written in another thread, I woke up about a month ago and found 3 molly fry hiding in my tank. Since I've never experienced one of my fish having babies before (as far as I know) I was very excited. Make a long story short, only one made it and he's swimming around in a 5g nano right now.
I've read that mollies can be very polific so I was expecting to see more swimming around. Its been awhile and I have'nt seen any. I have 2 female mollies and I've thought they were pregnant a bunch of times. I realize that the other fish in the tank will eat them, but I cant imagine that not one has survived. I recently ordered a nursary/breeder tank so I can put one of the pregnant mollies in it and give the fry a better chance at life. Is there any other way to tell when they are pregnant, other then a fat mid-section? I really cant believe that every time I've thought they were pregnant they had the fry but the fry were eaten.