Sexing Swordtails

[Mara M]

I have a swordtail that has no sword but has an obvious gonopodium. Is this a male or female?

[CorydorasEthan]

On 6/13/2021 at 6:55 PM, Mara M said:

I have a swordtail that has no sword but has an obvious gonopodium. Is this a male or female?

How old is the swordtail? All males have a gonopodium, though they take three or four months to fully develop their tail ornamentation. If your fish is older, maybe it is a fish that just happened to lose its sword? Or maybe it is a platy male, as platies look very similar to swordtails without swords. Any pictures?

[Mara M]

On 6/13/2021 at 10:14 PM, CorydorasEthan said:

How old is the swordtail? All males have a gonopodium, though they take three or four months to fully develop their tail ornamentation. If your fish is older, maybe it is a fish that just happened to lose its sword? Or maybe it is a platy male, as platies look very similar to swordtails without swords. Any pictures?

Oh ok. I get it. I'm not sure how old it is because I just bought it a couple of days ago, but its about an inch and a half now. I didn't know that it takes time for the sword to develop. That's good information. Thanks!

[gardenman]

Sexing swordtails is a lot of guesswork. Some males mature early and are easy to sex. Some mature very, very late and are much more of a challenge. I had a large female swordtail that I moved to one of my smaller tanks and she became a he. He/she was over a year old when he/she changed. We're talking about a nearly four inch long swordtail that flipped.  There are reports of female swordtails that have successfully spawned and had fry that later became males, so yeah, sexing swordtails can be a wee bit of a challenge.

[lefty o]

if it has a gonopodium, it is male.  some seem to develop their sword much later. some call them sneaker males, who knows why it happens, but it does.

[Beardedbillygoat1975]

I also recall hearing that the sneaker males tend to be bigger and genetically superior to the ones who develop their swords early. I know with my guppies and Endlers I’ve seen something similar where if they develop their colors later they’re a bit bigger and more robust. 

[Mara M]

So, I had post again.  I just noticed today that he now has a sword. As I said, I had no idea that it takes time. Again, thank you. That was some good information.

[Dancing Matt]

If you want some more info about swords. Look up Greg Sage (select aquatics). He has some good info about the swords he breeds and has talked about them in videos including the one Cory did of his fish room on aquarium Co-op's you tube channel.

[Mara M]

Thanks. I'll check it out.