The Confusion Between Pure Endlers, Hybrid Endlers and Guppies

Endlers, Guppies, What Are They And Why All the Confusion?

When Endlers where first introduced into the hobby they were often thought to simply be another type of Guppy.  This is understandable due to the similarities between the two species.  While Endlers and wild Guppies appear to be very similar at first glace there are some definite differences.

Some Differences Between Endlers and Guppies

Genetic Testing

Recent DNA and genetic testing has shown that Endlers (Poecilia wingei) have been reproductively separated from Guppies (Poecilia reticulata) for 500,000 to 5 million years.  This is similar to the genetic differences between a Swordtail and a Platy which are often crossed to produce some of the unique Swordtails and Platys that can be found in the hobby today.


male orchid Endler
Pure N Class Orchid Endler. Note the more streamline body shape as compared to a Guppy.

Male Endlers and male wild Guppies look very much alike to the untrained eye.  In fact feeder Guppies are often mistaken for Endlers. While wild Guppies and Endlers may look quite similar, male Endlers have much brighter and intense color.  Male Endlers are usually very colorful often having bright metallic coloration of orange or green.  There are also many other colors that can be found depending on the strain.

Most strains have a dorsal fin that is small clear and rounded however some strains can produce very colorful dorsal fins.  White dorsal fins are thought to be a sign that they are a hybrid however that’s not necessarily true as some strains like the Lime Green Endler have a white or very light blue dorsal fin.  The dorsal fin coloration and the length and size of the dorsal fin can be further enhanced with selective breeding.

The males of most strains have what appears to be a swordtail.  This swordtail is mostly just coloration inside the caudal fin however the sword sometimes grows outside the caudal fin.  The swordtail can be made to grow even longer with selective breeding.

From time to time a male may exhibit a swordtail that is much longer than most male Endlers growing out to almost a half an inch.  Long swordtails are often the sign of hybridization however the swordtail on the pure Endlers is much thinner.  This extra long swordtail usually takes several months before it can be seen that it is different than the other males.  We have seen this in nearly every type of pure N Class Endler we have kept however it does not occur very often.  Our experience has shown that this happens in about 1% of the males.

We have attempted to produce a line of Endlers that all have extra long swordtails using several different strains however the end result has always produced fry that grow to have a very small swordtail.

With the exception of a few strains female Endlers have little coloration on their bodies or fins. and look much like a plain looking female guppy.  Female Endlers in a few Endler strains exhibit black coloration on the dorsal fin.  There is also rare occasions where females may exhibit black dorsal fins or caudal fins where the strain usually displays clear fins.

Wild Guppies
By Per Harald Olsen – Own work, CC BY 3.0, Male & female wild guppies Note the thicker body and less intense coloration.

Body Shape & Size

Endlers tend to have a thinner body shape this is especially true around the rear portion of the body.  Guppies tend to be much stockier.  Use caution when selecting Endlers based on body shape as some hybrids look very much like pure Endlers in coloration and body shape.

Male Endlers are usually smaller than Guppies.  Female Endlers are often thought to be smaller than Guppies because they can produce young at a very small size however Female Endlers can grow to be every bit as large as female Guppies.


Endlers have a thin gonopodium that has one hook.  Guppies have a gonopodium that is thicker with several hooks.


One of the biggest things besides color that you will find with Endlers if their activity level compared to Fancy Guppies.  Similar to wild Guppies, Endlers are very active and tend to use every portion of the tank.  Male Endlers tend to do much more courting towards the females than do male Guppies which tend to be more aggressive towards females.

Pure Endlers vs Hybrid Endlers

Wild Type Albino Japan Blue Guppy
Note the thicker body found on this wild type Albino Japan Blue Guppy

A pure Endler is only Pure or N Class if it has absolutely no Guppy or other livebearer blood in it.  There are many who offer Endlers for sale on line as N Class Endlers when the images show they are clearly hybrids.  If it is important for your Endlers to be pure care should be taken where you get your Endlers from.  You may also want to make sure that there is documentation showing that the Endlers are the progeny of Endlers that came directly from Venezuela.

From a conservationists point of view it is very important to keep Endlers pure and prevent hybridization.  This is due to the constantly changing and limited nature of their habitat, predation and pollution, pure Endlers may be at risk of becoming endangered or even Extinct.  It’s quite likely that some strains have already been lost forever.

Endlers Exactly Like The Ones In The Wild

We sometimes get emails from people asking if we can supply them Endlers that are exactly like the ones in the wild.  Our answer is no.  Nobody can supply Endlers that are exactly like the ones in the wild unless the Endlers themselves came directly from the wild.

As soon as Endlers are allowed to reproduce in an artificial environment they start becoming slightly different than the original wild Endlers.  Why is this?  Endlers that are bred in captivity have a very limited gene pool to be bred from.  Because the Endlers are exposed only to a small number of other fish compared to in the wild the genetics also limits what the fish will become over several generations.  While the Endlers may look very similar to the ones captured in Venezuela they can never be exactly the same.

We want our Endlers to look as close as possible but better than the original strains they were developed from.  To do this we use images of the original strain as a pattern for our selective breeding process and do our best to bring out those traits that we like best from those photos.  We also work to try to make sure the colors are as bright as possible and try to make the patterns as well defined as we can.  Of course like many livebearers, Endlers are a highly variable species and no two Endlers are exactly alike.

Whether or not you choose to selectively breed your Endlers or not you are in a way creating your own line of Endlers based on the available genetics in your colony.  Our Endlers have their own special unique look that if you know what you are looking for you can see it.  Often we see images of Endlers on the web and think “those look like our Endlers” and after doing some research find out they originally came from our stock.

Mixing Pure Male Endlers From One Strain With Another

We’ve often heard that you can breed a pure male Endler from one strain with a pure female Endler from another strain and you would get a pure strain Endler that is just like the original male.  We don’t believe this to be 100% true.  It is true that when you breed a male Endler from one strain with a female Endler from another strain the resulting male offspring usually look like the original male Endler.  It is also true that if you breed a pure Endler with a pure Endler from another strain the resulting Endlers will also be pure.  These are sometimes referred to as Endler/Endler hybrids which are not actually genetic hybrids just crosses withing the same species.

Even if the resulting offspring look like the original male there has been other genetics that have been introduced into the bloodline making them different than the original males.  These differences in genetics may show up later in later generations.

Making Sure Your N Class Endlers Stay Pure

Trio of Albino Snake Endlers
Although the male in this photo is a smaller Endler size it is actually an Endler/Guppy hybrid (RREA Albino Hybrid Snake Endler)

First and foremost if you wish to keep pure N Class Endlers make sure you get them from someone that is reputable and can share with you the documentation of where the Endlers came from all the way back the the original ones that were captured in Venezuela.

Accidental Hybridization

It is our belief that pure N Class Endlers will become increasingly difficult to obtain in years to come.  Not only are Endlers being crossed with Guppies intentionally they also cross unintentionally.  Endlers can be accidentally crossed accidentally in several ways.  One of the easiest ways is to get hybrids unknowingly in the first place.  There are many breeders that are clearly offering hybrids as pure N Class Endlers and likely many more who believe they are offering pure Endlers when in fact their colony has been hybridized at some time without their knowledge.

There have been several accounts of accidental hybrids caused by Guppies jumping into a tank of Endlers.  This hybridization may result in a dramatic change in appearance or it may go undetected for some time.  To prevent this we make sure all of our tanks are covered with glass and any opening is covered with tape or something else.  We also make sure our pure Endlers and our hybrids are kept in different locations.

Another way that Endlers can become hybridized if you keep more than one strain (Endler/Endler hybrid) or if you keep other livebearers is from fry jumping out of a net undetected.  While netting an Endler it is quite easy to accidentally net some fry as well.  These fry can literally fly across a room and into another tank undetected as they try to escape the net.

Contaminating Your Original Line

If you have purchased a strain of Endlers from a reputable dealer and know that your Endlers are pure documented N Class Endlers, never add Endlers from a questionable source to your pure Endlers.  Remember any hybrids added to your colony will result in Endler hybrid offspring and they will never be pure Endlers again.

Is It Wrong to Keep or Create Endler Hybrids?

Many hobbyists believe it is wrong to create Endler Hybrids.  It is our belief that Endler hybrids are inevitable and creating and keeping hybrids should be done responsibly.  We offer several different hybrid Endler strains.  We try to make sure it is clear which Endlers are pure, which ones are hybrids and which fish are Guppies.

For the most part we don’t create hybrids as there are so many great hybrids being created by hobbyists all the time.  We have created a few of our own hybrids and have found that creating a stable hybrid strain can also take many more tanks than we have room for at this time.

Most of the beautiful Endler hybrids that we carry were created by other hobbyists.

We feel offering hybrid Endlers not only gives our customers a better selection but also helps introduce new hobbyists into the exciting world of Endlers and Endler hybrids.

Another reason we think hybrid Endlers are a good thing is it helps the genetically weak Guppy population to become stronger.  There are several new guppy strains being developed today many of which are actually Endler/Guppy hybrids.

Endler hybrids are here to stay however we feel hobbyists should be responsible and make sure it is clear to those who receive them know that they are hybrids.

Is my hybrid an Endler or a Guppy?

Like hybrids between Swordtails and Platys, whether or not a hybrid is called an Endler or a Guppy usually depends on what it most looks like.

Endler hybrids that are streamline and Endler size are usually referred to as Endlers.  Those that are more stocky or have large fins are usually referred to as Guppies.

Once again, just because a fish is called an Endler doesn’t mean it’s not a hybrid.



8 Responses

  1. teresajohns

    I would love to have these in my 10 gallon tank. I have 2 Neon Tetras and 1 Betta in there now so can I get 6 for a colony or is that too many for this tank?

    • Marty Andersen

      We have not tried Neon Tetras or Bettas with Endlers yet and we are not sure of how compatible they are.

      Neons would seem to be a good choice as the size is similar and Neons are usually great community fish.

      As with the Neons, Endlers are fast enough to stay out of the way of the Betts and would likely do fine however the additional activity in the tank may stress the Betta.

      As far as the number of fish goes you should be fine with 6 males as long as the tank is well cycled and has a good filtration system.

      We do not recommend adding female Endlers to the tank as they will quickly multiply and become too many fish for your tank.

  2. Teresa Johnson

    Thank you for your quick response and advise. I would like to keep pure Endlers as I am planning on getting a bigger tank and how many females would be okay 1 or 2? My tank is well cycled and I think these fish would be more interesting and more fun to watch than most others. Can I get away with 4 males for now?

    • Marty Andersen

      If you decide you would like to raise Endlers and are planning to get a bigger tank in the future I would recommend getting at least 3 females and keep more females than males. Males tend to bother the females too much if you have more males than females. We usually recommend 3 trios.

  3. teresajohns

    Can I keep 2 N Class Endlers and 2 N Class Snakeskin Endlers together? I don’t want to put any other live bearers in the tank, no guppies, no swordtails or mollies or stuff like that. Can Neon Tetras be bred by Endlers?
    I have been reading all I can and am confused about the N Class and the Pure Class are those the same thing?

    • Marty Andersen

      I’m assuming that you are referring to Orchid Endlers and Snakeskin Orchid Endlers. Technically they are both Orchid Endlers. The Snakeskin Orchid Endlers are simply a variation of the Orchid Endlers.

      If you were to allow the two strains to breed together the result would be pure Orchid Endlers (N Class) however the resulting fry would likely end up looking like one or the other strains or possibly a combination of both. My guess is that it would result in Endlers that would have a snake pattern but that the pattern would not be as pronounced.

      It would be a shame to mix the two strains together as there has been so much work done to make each strain as beautiful as possible. Although the two strains are technically Orchid Endlers, over the years they have become quite different from each other.

      Is it wrong to mix them? Certainly not as they are your fish to do with as you please.

      Of course if you were to keep only males there would be no possibility of them mixing.

      Oh yes, egg layers (tetras) and live-bearers (Endlers) cannot breed together so their would be no issues with them interbreeding.

      Care should however be taken to make sure the tetras will not nip at the Endlers.

  4. Teresa Johnson

    Thank you for your comments and I would like to order 2 of each as I have no desire or time to breed them. Do you have any idea when they will be available to ship? Will I be notified of their availability?

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