Are Swordtail Fish Born Alive?

Swordtails belong to the same taxonomic family as the guppy, family Poeciliidae. This family of fish is so well-known for giving live birth that it's called the livebearer family. Swordtails are indeed livebearers, who breed rapidly.

  1. Live Birth

    • Female swordtails can produce several batches of live young from a single mating, an adaptation called superfecundity. This -- coupled with frequent advances by male swordtail -- means that female swordtails are more or less permanently pregnant. Under ideal circumstances, female swordtails give birth to groups of up to 120 young every four to six weeks. The young are born looking like miniature adults, unlike some egg-laying fish whose larvae have different appearances from their parents'.

    Breeding Swordtails

    • As with many livebearers, swordtails breed so easily that the real trick is keeping them from overrunning the tank. The only real concern is that adult swordtails often eat their own young. In general, all you have to do is densely plant an aquarium so the young have hiding places from the mature fish. Plants make it more likely that at least some of the offspring will survive long enough to get big enough to avoid predation. If you want to ensure a large number of new swordtails, you can wait until a female swordtail is ready to give birth, then move her to another aquarium -- then back to the community tank after she has spawned. You can tell when a female swordtail is ready to spawn by looking at her abdomen. In a pregnant swordtail, a dark spot around the anal fin swells as the fish gets ready to give birth.

    Water Chemistry

    • Swordtails need a specific water chemistry to breed. Swordtails will breed only in somewhat hard, alkaline water with a tropical temperature. You need to keep the water between 68 and 82 degrees Fahrenheit. The pH must remain stable between 7.0 and 8.0.

    Caring for the Young

    • Unlike most fish, baby swordtails -- called fry -- do not need much in the way of special care. You should make sure no filters have inlets that can suck up the fry. Swordtail fry can eat ground-up fish flakes, though they appreciate baby brine shrimp. They also require more feedings than their adult counterparts to support their growth: Feed swordtails two to three times per day.