Select Aquatics of Erie CO.
                            The Swordtails  


   separate lines of wild and domestic swordtails of species X. alvarezi,
X. helleriX. mayae, and X. montezumae are currently being worked
with at Select Aquatics.

When chairman of the American Livebearer Association, it was pointed out to me that most hobbyists
    began keeping fish by raising guppies, platies, mollies and swordtails. Unfortunately, with all but the
    guppies, the other livebearers were created by crossing various species with one another to create
    colors and finnage generally not found in nature. The guppies, meanwhile, have been bred to look
    nothing like their native ancestors. The bright red, orange, yellow and green swordtails often seen in
    pet shops began as crosses between the X. helleri (one of the larger and more attractively colored
    wild swordtails) and primarily X. maculata (one of the wild platies). This process is described in
    some detail in "Swordtails... for the advanced hobbyist", Gordon and Axelrod, 1968, describing the
    first red swordtails seen by anyone in 1922. In 2010, pure swordtails or platies of any species are
    no longer seen in pet stores, yet many are as brightly colored and even larger than their pet store

    Through this careful breeding process the beautiful fish created by those efforts lost some
    aspects of their wild form, most notably the long (and on a few, very long) swords found on
    the X. helleri. Not found in the pet hobby are the swords carried by a number of wild species,
    such as the X. montezumae, X. clemenciae, X. mayae, X. malinche, X. nezahualcoyotl,
    X. alvarezi and X. signum species, all of which are kept today by specialty hobbyists.
    The swordtails I refer to here, and that comprise most all of the fish we generally think of as
    swordtails, will be from the Xiphophorus genus. For more specific information see
    "Atlas of Livebearers of the World".

    Well known to science, the swordtail Xiphophorus helleri was one of the first animals to have its
    genome fully mapped over the course of its use in cancer research. Various populations possess
    black spotting that through breeding manipulation can be triggered to become cancerous, and have
    been a resource for the study of melanoma since the mid 1950s. A number of wild X. helleri
    populations have been collected and introduced to the hobby, but many eventually disappear.
    Two recent introductions are being bred out here so that they can be maintained and kept in the
    hobby long term, the X. helleri Rio Otapa, and the X. Helleri guentheri Belize "Golden Stream".

    It is assumed that the long sword has been developed to attract females. In courtship behavior, the
    male will repeatedly swim around the female, who chooses to breed, in part, with the largest individuals.
    The sword extension seems to cause the male carrying it to appear larger to the female, resulting in
    increased matings with the males carrying the longest swords.

    There are also a number of swordtails with short swords, that are also very attractive but that are not
    very often seen in the hobby. These would include the X. cortezi, X. nigrensis, X. multilineatus,
    X. andersi, among others, including new species still being discovered and identified.

    Indigenous to Mexico, various species can be found throughout Central America, and at various
    elevations, though certain aspects of their husbandry can be assumed. They prefer clean water with
    some water movement as they evolved as wild fish in streams and relatively shallow water
    environments that also contain plants. Depending on species, the temperatures preferred are
    cooler than where they are generally kept by the average hobbyist, who was introduced to swordtails
    through those available in the commercial hobby. Most pet shop fish are kept between 75 and 80
    degrees, when in fact swordtails will grow larger, live longer and reproduce more consistently at
    closer to 72 degrees.

    Gestation is around 30 days for all swords, depending on temperature. Fry are about 6-7mm, and
    can take brine shrimp from birth. All swordtails are opportunistic fry eaters, and the females need to
    be removed from the adult population to have their young. A generation is about 8 months, and the
    young males do not begin to develop their sword until 3-4 months. Sexing young fish is done by
    identifying a gonopodium on the males, or the darker gravid spot area on the females. Mature
    males can be territorial with other males, and may spar and chase one another, though injuries
    are rare.

    It is thought that larger males release a growth inhibitor into the water that only affects other
    maturing males, though this substance, if it exists, has never been identified. When raising them
    to develop maximum size it is best to raise the sexes separately with generous water changes
    and abundant live foods, particularly red worms, black worms, daphnia and adult brine shrimp.
    See "How to Raise BIG Fish". However, you cannot take a fish that has grown up in a warmer
    environment and immediately move them into a tank that is 72 degrees, or the fish may become
    sick, most likely with a bout of ich, or "white spot disease". To accustom these fish to cooler
    temperatures, slowly acclimate them by lowering the heater in their tank by a quarter turn no
    more than once a week. You can then gradually acclimate them to cooler temps over time,
    avoiding disease. Be sure to accompany this process with regular water changes and
    frequent feeding. All of the fish raised by select aquatics are raised at 70-76 degrees,
    depending on the season.

    Swordtails are also rumored to change sex, which they cannot do. However, many species of
    swordtails produce early maturing males that sex out early, giving them a reproductive advantage
    over their siblings. Alternatively, the largest, dominant males take much longer to reach sexual  
    maturity, when overall body growth stops. Until then they may be identical to other females.
    Older females may also develop some secondary male sexual characteristics as they age,
    but they are never fertile.

    Swordtails and Size:

    Lastly, swordtails are often the topic of stories told regarding how big some fish used to be, or
    can get, or that someone once saw. I remember well growing up and hearing stories of male red
    swords bred in the 1960s that reached body lengths (not including sword) of 6 inches or more.

    Recently, I had a scientist friend who is well known in the hobby decide that he was going to raise
    an X. montezumae to the largest it can possibly become. It has been rumored that this fish can
    become 10 inches! He put no more than 3 males each in 2- 30 gallon tanks, fed them heavily on
    daphnia, various worms and dry food. At about 6 months, I flew out to East to see what he was
    doing and took pictures of them. See the pic of them here. They were becoming huge, fat fish.
    After about a year, he called me to say that someone had come to look at them, and estimated
    their length at 9 inches, though he did not measure them himself. He said he was about to destroy
    them because he needed the tanks they were in. I asked him to put them in alcohol and send them
    to me, which he did.

    I laid them out against a ruler, and they were 5.5 inches, from the tip of the nose to the end tip of
    the sword. They were very husky with a high back, giving them the appearance that they were much
    larger than they actually were. I have kept this species for many years, and now offer a population of
    Tomosopo monties here. They are routinely a fairly large fish (though not as large, or as brightly
    colored as the X. mayae), and over the years I have measured older specimens often. They would
    generally reach their maximum size at just about 5- 5.5 inches.

    I do not doubt that 6 to10 inch swordtails may exist in the wild, but I am skeptical that there were ever
    fish of that size in the commercial hobby. I have seen mollies raised to that size (about 6 inches)
    by a commercial fish farmer who also breeds his fish for size. If you would like to attempt to raise
    one of these swords to those large sizes that you don't see anymore, the X. mayae is an excellent
    candidate. Without question all of these swords are impressive in a show aquarium.

    And which species has the longest sword? Without question, the Xiphophorus montezumae,
    whose sword is routinely 1.5 times its body length, and will often sport a sword twice its body length!


                                 A Slightly different Approach to Buying Swordtails

    Raising Swordtails, particularly to get them to a large size, has led to unexpected issues. 
    Many of the swords sold here will routinely grow to over 4 inches, and some will pass 6 inches.

    Over the past 2 years we have attempted to raise large numbers of X. mayae, for example, that
    could be sold at about 3 inches, that were clearly going to be exceptionally large fish. We found
    that it is simply is not possible to keep the stocking levels low enough, the feeding schedule
    heavy enough, and still produce enough fish to meet orders. Many tanks of 40 and 50 gallons
    were tried to find the right stocking level to get the maximum growth from every fish in the tank
    throughout their lives. It was found that maximum growth continues only when they are moved
    to much lower density tanks at about 3-4 months old, and then fed heavily, with moderate aeration,
    adequate filtration, and water changes from that point on.

    For this reason, the X. mayae, X. montezumae, X. alvarezi and X. helleri populations will be sold
    primarily as recently sexed out pairs (4-6 months), or as groups of 6 young. The swords shipped 
    will be chosen for potential to become large individuals. Extras can then continue to be shipped
    with each order, and the fish will arrive at the best time in their lives to adapt to new
    conditions, while still young enough that their breeding capabilities are ahead of them. Most
    customers prefer fish of this size anyway, but for those looking for fully grown, older fish,
    I will have them available only occasionally.

    As full sized adults become available, they will be offered at Aquabid or by request.

    Selecting for larger fish as they reach sexual maturity somewhat guarantees that you are
    receiving fish with the potential to reach a large, healthy size. Nothing compares to fish raised
    under optimum conditions, and rows of tanks containing hundreds of fish, as is the case here,
    cannot duplicate what you can do with a few pairs in a 50 gallon tank, lightly planted with frequent
    feedings of quality food. I want to be sure the fish you receive have not had their growth slowed,
    or stunted in any way, so that with proper care they will grow for you as large as they are meant to.


                                 More on Size and Breeding Patterns in Swordtails

    One more point to mention is that a pair of large fish do not necessarily produce all young that will
    grow as large as their parents. This is especially true with recently wild fish, or fish that have been
    allowed to community breed over a number of generations. Careful selective breeding can develop
    lines that routinely grow large, but even then the variety of overall size attained by the males can
    span a wide range. Of a batch of 30 fry, say, of the wild X. mayae, for example, this is approximately
    what you will receive:

    Water temperatures and pH of the water in your fishroom will affect the ratio, but this species
    roughly produces 50/50 males to females. So we will assume there will be 15 males, 15 females.
    Since for right now we are interested in large males (and females are generally far more consistent
    in their growth and overall size), we will look at just the 15 males.

    - Of those 15 males 3 or 4 will be "early maturing" in that they will begin to develop a sword earlier
    than their brothers and cease overall growth for size at 4-5 months, topping out at about 3.5 inches.
    - 5-6 of them will take especially long to mature and with proper feeding and water changes will grow
    out to become very large fish. It may take 8-10 months for them to reach full size, and they will
    continue to slowly put on size throughout their lives. There are fish here that have lived for close to
    4 years. The largest male X. mayae here is the large very red male shown in the videos, and is 
    currently about 6 1/4 inches, including the sword.
    - The remaining 5-7 fish will be large full sized males that will top out at 4.5- 5 inches, and will be
    ready to breed at about 6 months.

    These ratios roughly work for most of the wild swordtails, including the X. mayae, X. montezumae
    and X. helleri. With the domestic lines, culling the early maturing males and only breeding the largest
    males, over a number of generations, does increase the consistency of production of large males.
    However, other traits often begin to appear, and the purity of the wild genotype will be lost, creating
    fish that become domestic, selectively bred versions of the wild form.

    I have had customers ask for "only fish over 5 inches", without realizing that not only are they
    requesting older fish, they are not truly receiving representatives of the wild fish they desire. When
    choosing the young, recently sexed out fish to send to customers, I do remove early maturing males,
    and choose those sent from those remaining. The fish sent out are chosen for overall robust health
    and good color. Swordtails require that large numbers are bred so that customers only receive the
    best examples, and of all those raised, easily a third will never be sold due to the natural variation
    in size and color that these fish exhibit.

    Customers write that they have been disappointed in the past with fish they had received from other
    breeders, in that they felt they were undersized, when in fact they were simply receiving fish that were
    born from from a pair or two the other breeder maintained, and the breeder simply sent what he/she had,
    and they were perfectly fine fish. I will always strive to send the largest, healthiest fish possible, but am
    able to do so because they are raised here in larger numbers. Over time we have gradually developed
    fairly large strains of the fish we maintain, but smaller fish and early maturing males are the normal means
    of reproduction for these fish, and as you breed them you will want to remove the smaller individuals that
    can influence the size of your line over time.

    I hope this clears up some confusion, as I wish to offer as many species as possible of healthy,
    full sized fish that live long lives after arriving in your tank! If you have any questions, simply
    email me at .


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             From Top:
            X. alvarezi
            X. montezumae
            X. helleri
                (Rio Otapa)
            X. nezahualcoyotl
            X. mayae
            X. alvarezi Albino




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