At what age does the sail fin and gonopodum show up on male mollies?

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-Kat

I'm not sure if this will help you at all. The woman at the pet store told me that you can usually tell after about 6 months when the fish has had time to develop a little more. When they are juveniles you cannot tell fully if they are male or female.

From my personal experience with mollies, I have been able to notice right around the 4-6 month age range. Also, if you look on the bottom of the fish you have now, the female mollie will have more of a fan like fin rather than a tube shaped fin like the male. The fan will look like one of those asian hand held fans and will be rounder in shape like a butterfly wing. Hope this helps you.

Good luck!

Let me think...

My first ever molly fry were born just before last Christmas, December 21, 2004 to be exact.

In February I gave some to my nephew that I thought were all female, but one later turned out to be male...Hmmm, how long was it before we could tell that?...

Somewhere around the 4 month mark. March-ish, from December fry.

And before the gonopodium formed they looked exactly the same, fanlike fins and all.