A swordtail fish is a livebearer, which means they have live babies.  At one time they can have between 10-60 babies but the average is 30-35 babies. 

 After giving birth, she can get pregnant immediately and will give birth again in a month.  If she is properly taken care of, she can give birth every month.  

A good ratio of male vs. female, there should be one male for every three females so you will have babies at least two times a month.  Just make sure that the little ones have plenty of places to hide as the parents will snack on them.

General Information About Swordtail Fish

  • Size:  Up to 5 inches
  • the pH of water:  7-8
  • The temperature of Water:  72-82 degrees Fahrenheit
  • Water Hardness:  9-15 degrees dH
  • Life Span:  3-5 years

Breeding Swordtail Fish

When a swordtail fish is three months, they are ready to breed.  It is very easy for them to breed because they are livebearers.  Just make sure that you are giving the babies a lot of floating cover.  If possible, put the babies in a separate aquarium or they will become a meal for the adults in the aquarium. 

Small frequent feedings, three times a day, will lead to better reproductive capability and faster growth rates.  You should have a breeding area for your little ones, which should be an aquarium that is 10 gallons or larger.

three swordtail swimming

The biggest threat to your pregnant females is the male swordtail fish because they can get aggressive toward them.  This can lead to stress for the female fish.  Do not keep the pregnant fish in a breeding box as there is not enough room for them to swim.  

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This can lead to abortion or early birth.  When your swordtail fish starts to slow down or stops swimming, it is time to move her to another aquarium.  She might also remain in one spot for a long time to sink to the bottom.  

Keeping the Swordtail Fry Safe

Most livebearers will eat their little ones and the swordtail fish are no different.  It is best if you have a separate aquarium for your new babies but if you do not, there are things you can do.

  • Use a large glass jar or big plastic container to separate your pregnant fish from the others.  Once she has had the babies, put her back into the regular tank unless you do not want her to get pregnant again.  Then you will have to put her in an aquarium with just other females.  
  • After she has the babies, you will need a breeding box.  It is a small mesh or plastic container that will float in the main aquarium if you do not have a separate aquarium for them.  With the breeder box, you will not have to worry about water conditions as you would in a separate aquarium.  The water will flow freely through the box but the babies will stay safe.
  • You should add some plants to the aquarium so that the fry will have more hiding places once they are out of the breeder box.  You can use live plants like guppy grass, water lettuce roots, etc will help to increase the survival rate of the babies.  The plants will help to cover them until they are large enough to start escaping from the adults.
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In four weeks, they will become juveniles.  Although this can vary from one fry to the other they should all turn into juveniles within six weeks.  At this time they are large enough to survive in the aquarium.  The adults may still be aggressive toward them so you will have to plant more heavy greens to keep them safe and provide them with hiding places.

Mating Swordtail Fish

When it is time to mate, the male will swim next to and nip the females continuously.  This can e stressful for the female and the male can wear them out with their continuing advances.  This is why it is important to have more females than males, generally one male to every three or four females. 

This will help to reduce the stress on the females.  If kept in large numbers in the aquarium, the males will become aggressive to each other at mating time.  Never overstock the aquarium as this will stress out the fish.

How to Prevent Swordtail Fish Fry From Dying

swordtail in aquarium
  • Water Conditions:  Although swordtail fish are resilient if the fry does not have the right water conditions they will die.  The water needs to maintain a temperature of 64-83 degrees F, the water hardness level of 12-30 KH, and a pH balance of 7.0-8.3.  If the water conditions are not kept right, it will take them over six months to achieve their full size or may never achieve full size.
  • Feeding:  Make sure that you are feeding them with care and not over feeding them.  They should have the ideal mix of proteins and vegetation.  Always be sure to remove any excess food from the aquarium after they are done eating.
  • Aquarium Size:  The aquarium where you are keeping the fry should be at a ten-gallon tank.  If they are overcrowded, it could cause them to stress out and possibly die.
  • Aquarium Filter:  They are so small that they can get caught in the aquarium filter and die so make sure that you use sponge filters to keep them safe.
  • Moving to the Regular Aquarium:  You can move them when they are about a month and a half to two months old.
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  • The male has a signature anal fin that is long and the female has a fan-shaped anal fin.
  • Swordtail fish like to eat live, flake, and freeze-dried foods.
  • In mid-life, a female can change into a male.
  • When your swordtail fish is ready to deliver, it is best if you move her to another  aquarium to deliver smoothly
  • When a baby swordtail fish is born, they are about one-fourth of an inch, and within three months, they will be one and a half inches.
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Hi! I'm Anna and I´m a certified cynologist (KAU, ACW). Expert, blue cross volunteer, owner of Chinese crested kennel "Salvador Dali" and breedless friend called Fenya. "I can't imagine my life without dogs and I totally support the idea #AdoptDontShop".