Animal Stories - Swordtail Fish


Animal-World Information about: Swordtail Fish

   The most popular fish next to the Guppy is most certainly the Swordtail!
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Trevor - 2014-09-15
Swordtails do not change sex, the situation you are referencing is a late developing male which occurs when there is already large male in the tank. Other males will develop slower until they reach a size that can compete with the tanks dominant male and will then develop their male characteristics. I have researched it and seen t twice in my own tanks, after which the late developing male would go on to father many fry of his own. This I am sure of from pairing the new males with young virgin females to be sure the changing of sex did not occur.

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  • Clarice Brough - 2014-09-15
    You're absolutely correct Trevor. Thanks so much for bringing this to our attention, we will adjust the information right away.
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imah - 2014-09-07
Hello I have a leopard pleco and I think it is pregnant so I have been doing some research. I needed to see if it was an egg layer or a live bearing fish. I searched it up and one site said that it was a live bearing fish and another site said that it was an egg layer. Also if it is a live bearing fish what are some signs to look for when it is about to give birth? I hope someone can help. Thank you.

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  • Clarice Brough - 2014-09-07
    Catfish are egglayers, as are the majority of freshwater fish species. Livebearers are mostly swordtails (like this fish), guppies, mollies,  and a few others. You can see an overview of livebearing fish on the main page of this Livebearer Aquarium Fish Atlas.
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Laura Cachia - 2008-07-24
I have a one-year old female swordtail (without a male) and believe it or not she had young ones!! I am wondering how this can happen, or it swordtails breed with other different species of fish who would be the father.

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  • jennifer Nickerson - 2014-06-22
    Swords mollys and platies once breed dont need a male to fertilize her for up to 6 months and will have fry 1time a month for 6 months with each birth she has the number of fry she has increases a older females thats had multiple births can produce a 100 fry each
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Meghan Dietz - 2014-05-17
I have some swordtails that aren't growing! I've had them for a long time, and you'd think they were grown-ups by now! Please help, I want to breed them! ~Meghan, 12 years old

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Dave reeve - 2013-11-03
I have two breeding pairs of swordtails but one of the males seems to like laying vertical in the weeds and even swimming vertical most of the time, is there a problem? Come feeding time there is no problem ......

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  • Clarice Brough - 2013-11-07
    There are many things that can cause a fish to show abnormal swimming movements. I would suggest the fish is stressed due to environment, but take a good look at the fish to see if you can identify anything unusual in its appearance. Abnormal swimming is often caused by Swim bladder disease (bacterial infection). More extreme problems could be parasites in the blood capillaries of the brain (Myxosoma) or nodules in the brain and spinal cord causing an abnormal position of the body and zigzag movements in swimming (Ichthyosporidium). As you can see, its hard to pin down, but swim bladder disorders are one of the more common illnesses.
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Anna Hermosillo - 2013-08-03
We have a Twinbar Solar Flare Swordtail that is giving birth right now and don't know what to do or how long it's going to take her. So far she had 2. How many will she have? Please help.

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  • Jasmine Brough Hinesley - 2013-08-04
    They usually have upwards of 80+ young! Has she had any more? The most important thing you can do is to remove the mother (and any other fish) from the tank or at least provide plenty of plants and other hiding places for the babies so they don't get eaten!
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Theresa - 2013-03-26
I have a Swordtail that I separated because she was about to have her babies. She had one that was born dead. About 2 hours later she had another stillborn. It has been 2 days and nothing else has happened. She still has the dark coloration like there are still babies there. But so did my Platty when she was done. Is it ever the case that it takes days sometimes for them to finish giving birth or can I assume she is finished at just 2 born dead?

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  • Jeremy Roche - 2013-03-26
    I have never seen 2 days but anything possible.  Any changes in water? Temp?
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janj - 2013-01-28
My dead swordtail has a worm by its gills. This is the second time it's happened, what is it please?

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  • Jeremy Roche - 2013-01-28
    Whats the worm look like?
  • Clarice Brough - 2013-01-31
    It sounds like your fish may have had anchor worm. The anchor worm (lernea spp.) is a true parasite that embeds in either the gill or body of a host fish. It can do considerable damage to its host, and it very contageous. This is actually a copepod (crustacean arthropod) rather than a true worm. It looks like a small whip (just a few mm to under an inch in length) with a forked tail. It attaches to the fish with its 'anchor' shaped head.



    For future reference... it is rather stressful for a fish, but the parasite can be carefully removed. Hold the fish on a damp cloth in your hand, then extract it with a pair of household tweezers. Gently press the tweezers as close to the skin as possible, but only extract the worm, not the flesh of the fish. Treat the infected area with an antiseptic (I've used iodine) after removing the parasite. Then return the fish to its tank.
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Bonnie Spielman - 2012-12-26
Do the female become infertile when they get older?

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  • Jeremy Roche - 2012-12-26
    Most will either loss fertility or slow down a bit.  A lot depends on health and environment.
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J - 2008-07-22
I'm wondering how people tell if the swordtails are pregnant, since I have 2 males and 3 females.

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  • Margaret - 2012-09-16
    The bellies of pregnant livebearers get very large, just as humans!
  • Jeremy Roche - 2012-09-17
    They will get large and you will be able to see the babies in the back portion of the belly there is a black spot that will expand as they grow!
  • Anonymous - 2012-12-07
    yes u can
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