Livebearers are all very hardy and are considered to be a good fish for beginners. Even so, the Livebearers are a lot of fun and many experienced fish keepers continue to delight in keeping them! There are lots of different varieties with lots of different colors readily available.
Many livebearers are tankbred and readily available. Rare species and wild caught species, however, are usually only available through aquarists' societies such as the American Livebearers Association.
Description: The livebearers are not found on all continents, only on the Americas and in Asia. Livebearers appeared late in the evolutionary process about 44-38 million years ago during the Oligoscene and Miocene periods. Like the adipose fin is a visual clue to a Characin, a visual clue to a livebearer is the pelvic fins of the male fish, the gonopodium. These fish have been in the aquarium hobby for a very long time. They were first introduced into Europe in the 1890's though rarer species have only been imported as recently as the 1960's. Livebearers have an advantage over the egg laying fish in that the young can immediately hide from predators from the moment of birth. The young of these fish are born live and almost fully developed, but watch the parents as they will eat their fry.
The Livebearers consist primarily of four families: The Poecilliidae family is commonly called the Live-bearing Toothcarp, in contrast with the Egg-laying Toothcarp, or Killifish. This family includes the Guppy, Molly, Swordtail, and Platy and is the largest family of Livebearers with close to 200 species. They originated in the Americas, but were then introduced into Asia and the Philippines to control malaria mosquitoes. They are now found in all tropical and subtropical areas. The Poecilliidae have teeth in both their upper and lower jaw, thus the name "Toothcarp" or "Toothed Carp". The Goodeidae family, called the Mexican Topminnow, includes about 35 species and is found on the Mexican plateau and the waters that descend from there to the ocean. The Hemirhamphidae family, known as the LIve-bearing Halfbeak, with about 20 species that are found all over Asia in both brackish and fresh waters. They sport a straight pike type body shape and have a beak type mouth. And lastly, the Anablepidae family, called the Four-eyed Fish, come from the coastal areas of Central and South America and are most often found in brackish water.
Social Behaviors: The Livebearers in general are not aggressive and are good community fish with other fish of similar size. There are a few exceptions from the Live-bearing Halfbeak family that are predators. Most livebearers are schooling fish and do best in groups of 5 or more. The schools generally develop a hierarchy with a dominant male that will be the most brightly colored fish in the group. It is best to have schools with only one male to several females. If you wish to have more than one male, be sure you add several extra females for each male to eliminate aggression.
Care and feeding: Livebearers generally enjoy harder water, and will benefit from 1 to 1.25 teaspoons per gallon of non-iodized salt being added to the aquarium water. Indeed, the molly is often kept in saltwater aquariums and is considered to be a saltwater fish! Also, some of these fish like the platy, the short-finned molly, and the swordtails are cold water fish and so can be kept without heaters.
Breeding: Because the young can immediately hide from predators from the moment of birth, livebearers don't need to be as prolific as egg layers; livebearers will commonly produce only 20-40 young although a few may drop as many as 150. See Breeding Freshwater Fish for a more information.
The females of the Livebearing families of Toothcarps (which includes the Guppies, Mollies, Swordtails, and Platys), Four-eyed Fishes, and Halfbeaks, through a process called "superfetation", have an amazing ability to store unused sperm from the male fish in her body for several months. The female is then able to have young several times after just one mating! A female Mosquito Fish was noted to give birth 11 times from just one pairing! Only the Mexican Topminnow livebearer does not have this capacity!