Breeding Guppies

There many, many different ways to involve yourself in the hobby of breeding guppies. Many people start out with an interest in the new fish they have acquired since they are beautiful and seem to reproduce with reckless abandon. As they start to save every batch of fish they possibly can, they soon find that they need more and more tanks. Often this guppy enthusiast will sell extra guppies to the pet store or trade for a few supplies to help support their "addiction". As time goes on, they may realize that, without a couple of ponds in the backyard, the work and space needed to raise fish for the pet store does not pan out, even though it was exciting and fun at first. All too easily, without having first started with quality fish from breeders, and trying outcrosses with unrelated fish, the fish they produce become deformed, and small. With some investigation, those that stay involved with the hobby become more serious and purchase quality breeding stock which breed true.

Insemination time

Purchasing Breeding Stock.

The first and most important thing to do is to acquire quality breeding stock. These are usually only found by a reputable guppy breeder. The guppies found in pet stores are usually commercially raised perhaps in Singapore (not specifically bred to be show quality) or are the culls from breeders' tanks (they may be labeled "Show Guppies", however this is a misnomer). In both cases the genetics inherit in these fish, which may be hybrids, usually take a lot of patience, tank space, work, and experience to create a line of fish that breed true and is truly regarded as "show" quality.

First of all, decide what colour suits you most personally. It is important to enjoy the beautiful characteristics of your particular fish - and you will be choosing this colour strain for possibly years to come! Quality breeding guppies are not inexpensive, but they are worth the initial investment. I do not recommend albinos for the inexperienced, since sterility and small bodies crop up continually without regular outcrossing. The line of fish you get should breed true and contain homozygous genetics (all the fish from each drop grow up to look like the parents). I recommend buying at least either a trio or 2 pairs. The male should show all the best characteristics, and be rather young as well. Younger males are more virile and show more interest in mating.

Receiving The New Fish.

Since guppies are usually shipped in a dark box for a day or two and undergo temperature changes in a small amount of water, they are naturally stressed and susceptible to disease breakouts. It is very important to make sure that your newly acquired guppies have a suitable environment in which to "stretch their legs".

A change in water conditions can cause considerable problems and perhaps dead fish. A sterile tank at least 5 gallons in size with an inside box filter should be ready to receive them. Consult with the breeder to get all water parameter information: does he/she use salt (at what concentration) as a regular additive? What is their pH? A rapid change in pH could spell disaster for guppies, and moving them from a salted environment to total freshwater can cause problems as well. Try to mimic the water the fish were accustomed to as much as possible. Some breeders recommend adding salt and/or formaldehyde, and/or Spectrogram antibiotic as a preventative. Consult Getting New Guppies for an explanation on how to slowly acclimate your fish to your water.

Since the sterilized tank with the new fish is not cycled, it will be necessary to monitor ammonia levels and remove a portion of water every day. In fact, it would be an excellent idea to set the tank up well in advance to getting the new fish and carry out a "fishless cycle" (More information on our Water Quality page).

Early Drops.

The female may be "pre-hit" - and ready to have a drop at any time. Your supplier should be able to give you such information. The father may not be the male that you were sent. It can be helpful because females that are kept from males too long can have a problem getting fertilized, especially with half-blacks. While some breeders recommend discarding this drop, I think it is important to save them. Other than the fact that the female could die from the stress of moving and delivering before she has another drop, the reasons are: You can not be certain that the male you have is not sterile; the father's genetics that sired these fry may be even better than the one sent to you; this "trial" drop may provide some genetic information (which itself should not be ignored) and possible back crosses in time to come. While it is possible the fry could have been damaged from X-ray equipment in customs, this should be apparent soon after birth and they will simply be culled in due time. If all the males of this drop appear very much alike, you can be assured that you have stock which breeds true (this should be the case if they were bought from reputable breeders). If the males are various sizes and colours, the drop should be culled, females included. Look forward to the next drop that your own male will sire. This may (I stress "may", as it is not guaranteed to work) only be accomplished if the male inseminates the female with his sperm within 24 hours of the drop (otherwise, the female's stored sperm packet will be those of the former male). Therefore, do not separate the female from the male after this first drop, even if she seems thin and stressed. After a day, remove the female so that she can enjoy some R & R and the best food you have to offer.

The Breeding Tank.

After about 20 days or so, the female(s) should be moved to a bare-bottomed breeder tank of 2.5 gallons to 5 gallons in size in order to receive the fry. While the gestation period is often about 28 days, it can range from 21 to roughly 40. This is dependent on a number of factors such as temperature and genetics.

There are different ways to set this breeding tank up; however the most important aspect is that the water be at least 50% of her original tank water to avoid any physical stress. Usually, one makes sure there are many hiding places for the fry when they are born, using plants, etc. Another way of setting up the breeding area is to obtain some netting from a fabric store and drape it deeply into the tank, secured at the edges of the tank so that the female cannot make it's way outside of it. The holes in this netting should be large enough for the fry to swim through to the bottom of the tank. Yet another option is to assume the female is not cannibalistic and leave no space for the fry to hide. Thus, they do not scatter for safety, and the female does not prey on them. I do not recommend the latter for your first drop. Many females are cannibalistic.

A popular device called a plastic breeder box, sold at many pet stores, is about the right size for a bagel. A slotted bottom (try to choose the kind with a V-Shape for fry safety) provides an area for the fry to fall through. Breeder boxThe problems with this are: You do not know when to put the female into the box except while she is presently dropping; putting her in it too soon may cause premature birth/abortion; she will be unduly stressed; most healthy fry attempt to swim toward the surface of the water, and a trapped female will often grab the fry; fry may be hurt/hang in the slots. This item is best used for emergencies when a drop comes unexpectedly.

A female that is heavy with fry may become rather still, due to a cumbersome body, and more stationary yet, if she is moved to a strange tank. You may see her vent dilate with close observation just before the birth. You can usually tell when the female has finished birthing since she will stop dropping fry at the rate she has and will appear about as thin as you would want her to be.

She should be removed after birthing, and watch for any possible stress. Birthing is difficult for some females, and sometimes their bodies stop functioning normally. They may hover and become still and then lose the strength to swim. There is not much you can do in such a situation except do your best with the fry that were born.

The New Fry.

Fry are normally hungry right after birth. However, they are too new to the world to know just how to find food. This is where a small tank becomes a very important tool in raising fry. They can find food more easily with a minimum of searching, which would simply waste their valuable energy. The food given must be tiny enough to fit into their mouths or it will be wasted and pollute the tank. Baby Brine Shrimp, newly hatched, is a popular food for new fry, however, it swims, and the fry must chase it down. It can also be bought frozen, which has the same nutritional content as live; the fry need to become accustomed to it slowly. Cooked egg yolk can provide a cloud of protein that the fry will greedily consume. Microworms are excellent for fry: they sink to the bottom, remain alive for days and give even more of a growth spurt than BBS. It is mainly the youngest worms that the fry will consume at this point in time; remove the larger worms from the tank which are left on the bottom.

Fry should be moved to a larger tank if they outgrow the one they are in. While a box filter and water changes help, crowding your fish will invite disease break-outs.


Culling is basically discarding the inferior fish from a batch of fry. They can be fed to larger fish, sold to pet stores, or in the case of serious abnormalities, destroyed. With good quality lines, culling is needed very infrequently. However, it is a very important function.

In newborn guppies there are sometimes tiny, darker coloured fry and belly sliders that cannot swim. These should be removed right away. About the 6th week of life you will notice that some fish do not develop properly in size compared to the rest; rarely do they become full-sized adults and should be considered culls. Slow development sexually is not cause for culling.

Separating the Sexes.

Fry can be sexed at one week of age, however, this is hardly necessary. When the males' anal fin becomes pointed, it is definitely time to remove the females (this may occur at 3 to 6 weeks of age). Use a small glass and either catch the fry in it or coax them into it with a net. Examine each closely for either a gravid spot or a developing gonopodium.


Young Purple Deltas

It is not absolutely necessary to separate the sexes if your fish breed true. Saving virgin females is important if you need to be sure of the father of your drops, however, it does take more tanks in order to do this. You may feel that in your breeding program you want more control over choosing parents; it is a choice you must make.

I like to leave a few females in the male tank for them to chase. This way, there are pre-hit females and virgin females available at the same time. I also feel that it is important for developing males to have females around to "practice" on. Young virile males need to vent their urges and the young females, I find, have no problem coping with their advances.

Choosing Breeders.

Choosing the females may be difficult since they show little of the genetic make-up that they carry. Females should have a nicely-shaped body that is also large and stout with thick caudal peduncles. Their caudals should have even colouration and shape. Colour is not really important. Overly coloured females do not generally throw very good males in their drops. Females should be used at about 3 to 4 months of age.

Males should, of course, show all the favourable characteristics you are trying to obtain. This is will likely include a nicely shaped caudal with good colouration and a dorsal fin that matches closely. They should have a good body shape and look strong and energetic.

Breeding Techniques.

Inbreeding: This is basically keeping a strain pure. The fish are kept closely related and brother and sister, father and daughter are routinely bred. A breeder will do this sometimes to fix a trait, such as a particular colour or shape. Mostly, you take the best male and female from the drop and breed them. Doing this can provide beautiful fish for years, provided the fish that you start out with are quality and you are lucky enough to choose not only the most attractive fish, but to pick fish as breeders that do not have an invisible weakness-for these will show up in the form of genetic defects, often looked upon as simply the result of "too much inbreeding". Take great care in choosing breeders; many times a strong body is the most desirable trait to keep an inbred line strong.

Line Breeding/Line Crossing: This method is also a form of inbreeding, however here you start by keeping the fry from two females (either from your new trio or chosen fry from a drop) separate, so that they form two distinct lines. Since you cannot mix batches, this takes more tanks. It is best to choose breeders differently for each line; for instance, in one line, you may pursue a large body mass, and with the other, you may concentrate on finnage. The purpose is to help maintain your established strain, since each line becomes distinct and more distantly related;  also, you can have your own two lines to cross occasionally. When you want to increase the size in your fish, for instance, or make an outcross to avoid too much inbreeding, taking someone else's line to do this with is risky and you may loose the traits in your line that you have worked hard to achieve, as well as loosing the homozygous quality of your guppies.

Out Crossing: This is the opposite of inbreeding - the mating of fish that are unrelated to other. This creates what is called a "hybrid" guppy. "Hybrid" vigor may be seen in such fish-outstanding size, colour, and health. The genetic patterns of the parents are scrambled/mixed up, and such fish may be good for show but not for breeding. An outcross with a fish that itself is only a few generations ahead of an outcross may produce beautiful fish for a few generations, but the loose gene patterns will turn them eventually into a fish resembling the small, original wild guppy usually sold as feeders in pet stores. Although this is, of course, how new strains are produced, it takes much time and knowledge of genetics to create a pure strain. Thus, it is not advisable for the novice to attempt an out cross in order to fix a strain.

Most breeders stick with line breeding and do their best to choose fish to breed with that have the characteristics which they think will improve their lines, while keeping their guppies breeding pure.

It's important to remember that guppies react differently with various methods of care, water conditions, and breeding methods.  What works for one person may not work for you when trying to breed the exact same line of fish.  Every strain varies in it's own needs and rate of development, as well.  It takes years of attentive care and analyzing breeding techniques to find out just what works for you and your guppies.  This is what makes guppy breeding the fascinating hobby it is!

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