How Old Are Fish When They Start Breeding?

[sussexgirl]

My mum's got some platy fry that are approximately 8 weeks old. My dad thinks that one of them is pregnant already but mum's insistent that she's just fat.

How old are fish (especially platys) when they first start to breed?

 

[SPLiSH]

It varies greatly with species. Platies are mature and ready to breed at three months of age.

 

[voo]

Platties do mature very quickly, some of my platty fry area already pregnant and they are no bigger than 2cm.
It is very unlikely that you would have a fat platty that wasnt pregnant. It might not appear black at the back until the eyes have developed.

Are you able to tell the difference between male and female platty? If it is female its almost certainly pregnant.