Adult platy females are usually a bit larger than the males. Juveniles can be hard to sex - sometimes I am able to tell by 4-6 weeks, sometimes much later. Also, 'old' female platies can (but not always) appear more like males than females.
Adult platy females are usually a bit larger than the males. Juveniles can be hard to sex - sometimes I am able to tell by 4-6 weeks, sometimes much later. Also, 'old' female platies can (but not always) appear more like males than females.
There are sub-dominant males (aka late bloomers) in Swords and Platies. They look like a female and then all of a sudden they develop a gonopodium (spelled correctly) when they are a large fish. It's not a sex change, just late sexual maturity.
Another little factoid Swords when male swords develop theirs, that is pretty much the max size they will be. If you take care and do daily water changes and don't crowd them, you can get sword females that are 6" long and males in the 4-5" range (before tail). It's amazing what water changes will do.