How to identify male from female...

[ronnfive]

How to identify male from female:

Swordtail (Xiphophorus helleri) – this type of livebearers are easily sexed through observation. The male Swordtails have swords on their tails while the females do not. Usually the female is larger and has a rounded body than the male. Generally, the best observations are focused on their “gonopodium” or what we called the modified anal fin. It is a tube-like fin at the lower backside next to the belly of the fish.

Guppy and Endler (Poecilia reticulata/Poecilia sp. endler's) – this type of livebearers are easily sexed through observation. The male Guppies or Endlers are smaller and more colorful than the females. Generally, the best observations are focused on their “gonopodium” or what we called the modified anal fin. It is a tube-like fin at the lower backside next to the belly of the fish.

Molly (poecilia latipinna) – this type of livebearers need more observation than the other livebearers. The common male Mollies have a colorful tail (like bluish or greenish color) having a larger dorsal fin, and is usually thinner (viewed from top) than the females. Generally, the best observations are focused on their “gonopodium” or what we called the modified anal fin. It is a tube-like fin at the lower backside next to the belly of the fish.

Platy (xiphophorus maculatus) – this type of livebearers needs careful observation than the other livebearers. The male Platies are typically smaller or thinner than the females. Generally, the best observations are focused on their “gonopodium” or what we called the modified anal fin. It is a tube-like fin at the lower backside next to the belly of the fish.

Here is the male’s gonopodium

A closer look…
Gonopodium

Here’s a female
Anal fin

A closer look...
Anal Fin

Hope you find this useful...
Ronn

Please feel free to correct me, if I’m wrong or add something... so that this will be very useful to the others or new into fish keeping of this type of fish. Thank you.

[Lydia]

Good info! Maybe this should be made a sticky or put in the articles section?

[TheOldSalt]

Done!
We get this question so much it's high time we had a sticky for it.

[ronnfive]

Thanks much! Hope this will help a lot of people who's into this type of fish. This is a great fish and very hardy.

ronn

[apple]

http://public.fotki.com/apple1/fish/ is my gold molly in the breeding nest a female lol i hope i didnt pu tthe wrong fish in the breeding nest lol

[tonkstoy2003]

Okay with the swordtails, only the Males have the sword? because I can sex the fish, but the lps told me that the two i have the one with the sword was the male and the one w/o it was the female, what puzzles me about this is the fins on the bottom are the same in both. they both have the same fins underneath just like my mollies. That's what i was confused about :P Thanks

[ronnfive]

Pic would help a lot...

All livebearer fish born females, then later on when they are old enough or about 2 months old or so, some of them decide to change gender and some continue being females. One of these situations is that sometimes this type of fish decides so late… and later on shows gonopodium and in your case swords. A late bloomer fish, what we called it…mostly they grow quite large that they looked often mistaken as female. I hope this help!

-ronn
ronn.gfxartist.com

[Steve155]

This is great! Thanks!

[tikotaz]

I have a male and female creamsicle molly they have similar dorsal fins though the one in a seperate tank is smaller. But underneathh it's hard to tell, they look similar as well and I can't up and squint to see if the one in the seperate tank has that part, though belly is getting bigger each day. Was told that it was a female, yet still not birthing yet.

[cocomania]

Great job, I will deffinently keep all of this in mind when i start buying all of my fish.

[elvis332]

RONNFIVE YOU ARE RIGHT I HAVE A SORDTALE AND THE MALE HAS A BLACH SKINNY LINE IN ITS TALE

[vettech909]

great info!!!now i know i have 2 females and 1 male

[audzter]

Nice info!!!

[Manthalynn]

Scientifically speaking, what causes them to decide to become male or female?

Is it physiological, ecological, or environmental (those last two might be the same...)? I'm curious about the cause because this happened (I think) in my 10 gal tank. Maybe "s"he is just a late bloomer.

I purchased a male and female swordtail about a month ago. I can definitely tell the difference between male and female livebearers but I think I was distracted by the one having a long tail and the other having a short, blunt tail. The more I looked at it I thought, now that's confusing, that looks like what I would expect to see on a male.

Tonight after moving a lot of things around, I just noticed that the "female" is starting to get an extended tail! That clears up my gender confusion, I guess.

To aid with the discussion, I have waaaay too many other livebearers in this tank so I wonder if it's a sort of darwinian pressure exerted from the others. Although I always thought it was the males supressing the other males from developing.

[ThatFishKid]

I noticed to my dismay that a group of livebearers was left out: Halfbeaks! I can't seem to determine weather or not there is a "modified anal fin" on the males or not. Size difference is the only thing i know of.