Breeding Livebearers

Breeding livebearers

This article will detail breeding methods and tips for the four main species and sub-species of livebearer found in the hobby. This includes the guppy, platy, molly and swordtail. Livebearers originate mostly from Central America and parts of North and South America.

male blue with black spots
male guppy showing fancy finnage

Unlike other fish, livebearers employ a form of copulation to reproduce. The male develops a specialised fin called a gonopodium which is used to mate with. The gonopodium is motile and can be manoeuvred towards the vent of the female whenever she is within range. He uses his organ to deposit a pocket of sperm into the female’s sexual opening.
The female will only use a portion of this sperm at a time. She will store the rest in her fallopian tube to fertilise later batches of eggs.

Although hobbyists never see the eggs, they are quite large with a large yolk to feed the embryo. The developing embryos also take some nourishment and oxygen from the mother while they develop.
The embryos hatch from their eggs as they are being born out of the female’s vent.

These days, most livebearers in the hobby are propogated through selective breeding. Wild type livebearers being very rarely obtainable. The wild type livebearer are hardy and excellent beginner fish. However, the genetically purified breeds found in most pet shops are not so hardy. So, the guppy and platy might not be considered a beginners fish anymore because they can fall ill when water conditions are not perfect.

All varieties and types of guppy will interbreed, as will all platys and swordtails (including the variatus type), as will all mollys (including the sailfin molly). Therefore, if you want to breed and sell high quality livebearers then you should keep just purebreeds while keeping other breeds in separate aquaria.

Some adult guppys and platys with fancy fins cannot mate because the gonopodium also being a fin will be malformed. Such males can only be bred when they are relatively young before the fins are fully formed. Or, alternatively, artificial insemination has to be employed.

dalmation molly male
farm produced dalmation molly male

If you are starting from new then you will need to buy some purebred livebearers. The best place to do this is from a local breeder. Don’t expect the breeder to sell you his best fish. However pick several of his best rejects. The more you buy the better, you will have more to work with in trying to resonstruct the pedigree. Alternatively you can buy from a pet shop. Some mass produced livebearers are occasionally quite good. Don’t buy if you see a mixed aquarium with different coloured fish. Note, this will involve more work to establish a good quality strain. Another source of fish is the live fish section on ebay. Here great care must be taken before buying because you may not see the actual fish before you buy and there is no guarantee as to the real pedigree.



Selective Breeding

pedigree red guppies
pedigree red guppies

To do selective breeding, you need`several aquariums. A fry tank should have a temperature of 79F, which wil speed up growth. Adult tanks can be kept at 73F. However, for the sunset platy all temperatures should be 5 degrees less. In a tank of young you must separate out the males as soon as they develop the gonopodium. For guppies this can be from 3 weeks onwards. The search for males must continue daily because some males develop late. As time progresses you will have two tanks, an all male tank and an all female tank. When the fish become adult sized they can be moved to the larger adult aquaria.

Males that develop early should not be used for breeding because the best males with better fins, size and coloration take longer to mature. These late maturing males are sometimes mistaken for females.

You must also weed out any runts and any fish with the wrong fin shape, body shape or colour. This must be done as often as possible collecting all unwanted fish in a separate aquarium. You can then sell this group of fish to the pet store or sell them via classified ads on the internet or local paper.

What you will need for breeding

3 18inch aquaria
2 larger aquaria (1 full of males, 1 full of females) for every breeding group. If you have two breeding groups then you will need 4 larger aquaria.
sponge filter
fine leaved plants or plastic plants
plastic grate
1 male and 2 or more females of the same breed

Pick out the best male in the male tank with 2 best females from the female tank.

Place the chosen breeding group in an empty 18 inch fry tank. Feed well with plant matter and live food. Raise the temperature to about 79F. Sunset platy 74F. The ideal ph is 7.6 and the ideal hardness is about 20dh. Mollies prefer a little salt as well.

Leave the group together until there are clear signs the females are pregnant then remove the male.

Place the pregnant female who is close to giving birth in a heavily planted aquarium or employ a grate where the young drop through but prevents the mother from following. Alternatively, add plants to the original aquarium to provide shelter. Include a sponge filter. Be very careful not to stress her.

The birthing aquarium must be a mature aquarium using water from an established aquarium. To recognise the female as close to giving birth look at her abdomen. It will look quite squarelike with the front of the abdomen becoming as large as the back of the abdomen. She will look as if she is about to burst. After birthing remove the female and the grate. The fry are ready to eat soon after being born and do best with a mix of powdered dried food, live food and plant food. The fry are large compared to most egg layer fish.

An air powered sponge filter along with daily partial water changes while feeding several times a day will ensure the best growth rates. Always carefully remove any uneaten food when it occurs. When the fish mature they can be separated into males and females.

If most of the resulting young are looking promising then re-use the same parents to breed from again. However if most of the young are disappointing then don’t use the same parents again. Here it is quite handy (almost essential) to keep a record of which fish you breed.

Line breeding for ongoing selective breeding

Line breeding is an essential technique to maintain a long term viable breeding program. This is when the breeder maintains two or more separate breeding groups. Every few generations breeding is allowed between the 2+ groups (known as lines) to maintain genetic diversity. Having just one breeding group will after a few generations result in a narrow and weak gene pool with the resulting young becoming weaker and weaker.


Outbreeding to restore genetic vigour

original wild green swordtail

If or when the the breeder’s breeding stock becomes weaker through too much in-breeding then out breeding has to be done. The breeder will have to obtain an unrelated fish to breed with his pedigree fish. This should idealy by a fish of the same breed from another pedigree breeder. If this is not available then any unrelated fish has be chosen which makes the task of getting back to pedigree harder. Then it is a matter of over the next few generations trying to regain the original pedigree whilst retaining the new vigour. Wild type livebearers are ideal for this because they have the greatest genetic diversity and so add the most new genetic material, leaving you with strong pedigree fish.



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