How Young Can a Fish be Vented Accurately?

MonsterCichlids75

Gambusia
MFK Member
Feb 15, 2012
347
0
16
Boston, MA
vieja maculicauda and vieja synspilum in particular…I have 2.5" - 3" juvies of both and i was wondering if they are old enough to accurately sex by venting? Also, just looking at them in the tank, some have a longer, curved, and more pointed "genetalia" and some have a smaller slightly more blunt one…the ones with the more rounded, are those females are is there a chance they could be male and just aren't sexually mature?
Thanks everyone!
 
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