Sexing Platy fry

[OohFeeshy]

How old is it before you can rasily sex platy fry? My friend is giving me some and she can't tell the sex, but i obviously want a 2:1 ratio.

 

[mrplaty]

I think it is at about 6 weeks to 3 months

 

[Fiori]

My first platy fry are now about 10 weeks old and I think they are just starting to show some signs of sexual differentiation.

 

[vidiots]

You will find that they all seem to grow at different speeds. I think the females tend to grow the fastest, followed by the fast growing males, then finally by the slow growing males. The problem is that under 3 months old it is often difficult to tell the males from the females, cause they all look female. However you should be able to tell even the slow growing males from the females by 6 months and by that time the females and fast growing males are capable of breeding. I have heard that the slow growing males tend to be larger than the fast growing ones once they reach full size, but haven't verified this myself. If you want to prevent them from breeding until you want then too, you must seperate the males as soon as you are capable of positively identifying them as male. The slow growing males are what make early identification difficult since they appear female until they mature.