Livebearers

Posted December 7, 2009

Livebearers are perhaps the most common of all aquarium fish. They are, together with the ubiquitous goldfish, the most common beginner fish. This is due to the fact that they are hardy and easily spawn in community aquariums, giving the keeper the joy of watching fish babies. They are also very cheap since it is easy to breed them in large quantities.

There are a lot of different livebearers but only a few species are common in the aquarium trade. Most of the species that are common in the hobby looks very different from their wild cousins due to having been selectively bred in captivity for so many generations. Two examples of this are the guppy wish is much smaller with smaller fins in the wild and the swordtail which is a green, not red, fish in the wild. Another example is that the black molly was formed through line breeding; wild mollies are not pure black. The wild versions are often very beautiful in their own right and often hardier than their line breed counterparts. If you encounter the natural form of these fish it can be well worth giving them a chance.

Live bearers are often recommended to beginners and many of them do make good beginner fish, but there are other species that are even more suitable as beginner fish. The livebearers where once the ultimate beginner fishes but they have become much more sensitive over the years due to continued development and mass production of fish. I do for instance not recommend the black molly to beginners anymore as it today unfortunately can be a quite sensitive fish.

Many of the most common livebearer species in the trade belong to the family Poeciliidae. In this family, you will for instance find the well-known molly, platy, swordtail, and guppy. Another commonly kept family is the family Hemirhamphidae where you will find the popular halfbeaks.

Most livebearers and virtually all commonly kept livebearers are ovoviviparous, i.e. the young develop from retained eggs inside the body of the female but the eggs are independent from the mother. There is however some viviparous species as well; their young get nutrients directly from the mother through her blood which runs through structures that can be compared to a placenta. The halfbeaks are for instance viviparous while all Poeciliidae specis are ovoviviparous.

It should be noted that some species of fish, e.g. the South American freshwater stingrays, aren’t considered livebearers in the traditional hobbyist sense of the word even though they give birth to live young.

Livebearers are best kept in aquariums with a lot of plants along the sides and back and open space in the middle to swim in. This is generally true for all livebearers although some livebearers prefer more plants than others. Livebearers can be kept with other small non-aggressive fish species.

Most common live bearers are easy to breed and often spawn spontaneously in community aquariums. Some fry might survive in a community aquarium but most will end up as food. If you want to save your fry you can move the female to a breeder cage or to another aquarium. You can also move any fry you see to a breeder cage or another aquarium but this will never be as effective as allowing the female to give birth out of harms way. The female will eat her own young and will show no care for the fry once they have been born, so get her away from them as soon as possible after the birth. The fry grows quickly.

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