Sexing Mollies

[BottomDweller]

I've just got a silver molly who looks like a female but is quite thin. I know all mollies start off looking like females and then the males' analfin turns into a gonopodium. I was wondering how big do mollies have to be before you can tell gender for sure? Mine is about 1.5" long including tail. Thanks

 

[AJE]

I have males and females that are visibly males or female under an inch, maybe it depends on the type of molly

 

[BottomDweller]

Thank you. I guess she's just a skinny girl then. It doesn't matter too much what gender she is since she's the only molly in the tank. I was just curious.

 

[emeraldking]

With mollies the analfin transition can happen at different ages. Overhere, I've got male mollies that have developed a gonopodium when they were just 1 inch but also at 2-3 inches of length. So basically, hard to tell beforehand at what age a gonopodium will develop.
If a group of mollies is exsisting of mostly females, most likely a small juvenile male will develop its gonopodium faster but his bodysize will remain smaller. This is just to ensure reproduction within the colony.
But this also happens with other kinds of ovoviviparous livebearers (swordtails in general).