I have 7 platy/swordtail fry that are 12 weeks (3 months) old and they aren't showing any sign of gender. When should I be able to determine the sex? Thanks a ton
The males should start developing a gonopodium at 4-7 months, some may be late developers. They will probably be at least 2cm long before you can tell.
it could be that the males are releasing a hormone to prevent others to grow larger than them. do a 15% water change daily for them and see if that helps the development
In my experience feeding live baby brine shrimp and other live foods along with at least a 20L tank excelerates their development. I can always sex mine at 3 months. I typically keep 6 or so large female Endlers with my sword fry as a ready source oflive food-Fry.
i thought i had all females until this week! these are pushing 7 months old! mine were late developers! Mine are like the kids who have a high voice until they are 16 but then change almost overnight! mine developed from almost no color to almost full color in 2 weeks! The gonopodiums just developed recently too! every fish is different