Breeding Swordtail(Xiphophorus helleri)

Swordtails are viviparous fish, which means they are livebearers; unlike ovoviviparous fish which lay eggs. The male fertilizes the female's eggs internally. The fry then develop within the female. As the fry begin to develop the female develops a gravid spot, located near the anal opening. With my pineapple swordtails it is reddish. Livebearers will generally have 1-60 fry per spawn. When the fry are born they are immediately free swimming and will begin to look for food. If they are not removed from the tank they will become food for mommy and daddy or most other fish in the tank. When my pineapple swordtails had fry, they had approximately 30 fry in my community tank, but because of bad timing I didn't have a chance to recover them that day and could only save 9, which I keep in a mini-desk aquarium with an air stone and a simple under gravel filter system.

Editor's Note: there are cases where the fry are not free swimming when they are born. Sometimes, for different reasons, the female may release the fry early. These fry that are not quite ready to swim yet are usually referred to as "sliders". They will resemble fry recently hatched from eggs and not completely developed. These fry are often not hardy and perish much more easily than free swimming livebearer fry.

To ensure fry survival once removed I have set up a 5 gallon aquarium with a sponge filter. For my temporary aquariums, I use dirt magnets, which you can get for around six dollars at most retail pet stores. Do not use a power filter or the fry will be sucked up. You can also put the female in a breeder net in the main aquarium until she gives birth. After the female gives birth remove her or she will eat the fry. The fry will begin looking for food immediately. You can feed them prepared foods like Hikari First Bites or infusoria; baby brine shrimp also work well as a starter food. I feed my baby swordtails a Spirulina flake and Color Enhancing flake mix ground into a powder. After About a month and a half the fry should be big enough to rejoin the community tank without being eaten.

Editor's Note: although sponge filters are highly recommended for their safety and biological efficiency in a grow-out tank, power filters can be used as well. A sponge or other covering for the intake tube will help slow down the water flow and prevent the fry from being sucked into the filter. Also, in most cases, livebearer fry are large enough to accept crushed flake foods and don't require tiny foods such as First Bites or newly hatched brine shrimp.

About a month after the first batch expect another batch from the same female. Female livebearers store sperm in a pouch for several months and can continue to have fry without being near another male.

Temperature: 78
pH: 7.6
water hardness: 75
Salt: Approx 1 teaspoon per 5 gallons.