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Livebearing tropical fishes as so called because they do not lay eggs. They give birth to live, fully formed, and free-swimming fry. Examples of livebearers are the Guppies, Swordtails, Platies, and Mollies.

The eggs of livebearers are fertilized and develop inside the body of the female, making the count of offspring relatively low – up to 50 per spawning. However, livebearing females have a unique capability to store sperm, which allows them to develop several successive broods from just one mating session.

The male has a gonopodium, a sex organ derived from several rays of the anal fin. When mating, the male directs its gonopodium towards the female and while briefly attached to the partner’s cloaca, the gonopodium releases and channels sperms into the female.

Once fertilized, female livebearers will nonchalantly give birth to their fry even in a community aquarium, with successive broods born as often as monthly. Unfortunately, the fry, being very small, become easy prey for other fishes, including their "parents". Fine-leaved plants offer good hiding places for the newly born, but not very many will survive to adulthood in a well-populated fish community. Which is why a specialized breeding tank is recommended for livebearing species.

Transfer the female, when she's about ready to drop her young, to a breeding aquarium rigged with breeding traps (plastic ones are commercially available) that will separate and safeguard the young. You can use layers of fine-leaved plants or patches of Java Moss where the offspring can hide. After the female delivers her brood, return her to the community tank and care for the fry separately.