Not sure sex of my platy

I'm a newbie. Just bought two platies from pet shop to start my new tank. It's meant to be two male ones. When we came home with light on, we realised my Micky could be Minnie. I did some research online and learnt the difference. But still not sure if my platy is female or male that not fully grown up. Please help. Sorry if it's a daft question.

it looks like a young male.

An adult/ mature male livebearer's anal fin is long and pointed and called a gonopodium. The female's anal fin is fan or triangular shaped. Young males will sometimes show a fan shaped similar to yours, but the fin is longer and as the fish gets older it will look more normal. Young females will show the typical fan/ triangle shaped anal fin all the time.

Welcome to the forum, OnePenny (You're not a Terry Pratchett fan by any chance, are you? I am pronouncing your name as 'On Epen Ny' in my mind )

It's not a daft question; whilst mature, adult livebearers are easy to sex, the fact that the males start off looking female and develop their male characteristics later, does mean there can be uncertainty about some fish in the 'in-between' stages.

I would say your fish is a young male that hasn't yet developed a full gonopodium; that's the technical name for the modified anal fin they use for mating.

Edit; I see Colin's a much faster typist than I am, lol

Thanks for the replies, guys. Now, I feel really relieved. Apart from the appearance, I was concerned that Micky was a female, because as soon as we transfered Micky into the tank, my other platy Liam kept chasing him like mad. It was like a male chasing a female trying to mate. But Liam seems clam down a lot today. That's another reason why I wasn't sure. Many thanks. Btw, I'm not a Terry Pratchett fan.[emoji28]

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if you only had 1 platy in the tank before adding Micky, then the older platy (Liam) would have thought he was an intruder and either wanted to be friends or chase him out of the territory.

OnePenny said:

I'm a newbie. Just bought two platies from pet shop to start my new tank. It's meant to be two male ones. When we came home with light on, we realised my Micky could be Minnie. I did some research online and learnt the difference. But still not sure if my platy is female or male that not fully grown up. Please help. Sorry if it's a daft question.

Click to expand...

Definitely a male

Thanks, everyone. I feel a lot more reassured now. And really happy that I don't need to go back to the shop and swap Micky as I am attached to him already.

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