Differentiate red F molly(non-balloon) vs. red F swordtail

tigerbob

Exodon
MFK Member
Oct 28, 2019
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I've read several articles and posts on the internet and none of them give definitive way to tell the difference from female molly to female swordtail. I can tell the fish is a molly if it's white or black or balloon shaped or having sailfin, because these features only appear on molly. But for the red females, I can only see that the red mollies are usually a bit more orange than swordtails.

Today I went to a LFS and watched in front of a tank of mollies and a tank of swordtails for ten minutes and still couldn't reliably tell the difference. The shopkeeper wondered what I was looking at so I asked her. But she said those fish are of the same species lol...
 

Jshgre

Feeder Fish
MFK Member
Jan 2, 2020
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In my experience, Mollies are more rounded especially mid body.
Swordtails have more of an elongated body including base of tail
 

tigerbob

Exodon
MFK Member
Oct 28, 2019
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I agree that molly is usually thicker near the tail. But this is difficult to compare when fish are moving and when individuals vary in shape due to their nutritional condition.

For instance I find on the internet a picture for swordtail and one for a pair of mollies. The females are indistinguishable body shape wise, at least to me.
Screenshot from 2020-01-03 23-14-05.png
Screenshot from 2020-01-03 23-14-20.png
 

Jshgre

Feeder Fish
MFK Member
Jan 2, 2020
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Definitely a very visually similar species nonetheless. I've never really had the separate the 2. Each having their own tanks. But I could see it wouldn't be the easiest to pick the 2 in a tank full of same coloured female Mollies and Swordtails.
I forgot to add. From wild specimens, I've noticed Mollies tend to have a more rounded fan shaped dorsal and slight difference in scales, with Swordtails having smaller thinner scales. As you can more or less see from the photos.
Nonetheless from generations of inbreeding and hybridisation of many livebearers, I can see how getting exact differences between the two will be very difficult.
 
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