Select Aquatics of Erie, CO

                      Keeping The Xiphophorus montezumae


          Basic Stats:

      Size tank- 10 gallons or larger

         pH - 7.0 - 8.2

         Hardness- Moderately hard

         Filtration- Heavy filtration

         Aeration- Moderate to heavy

         Water movement- Yes

         Nitrate tolerance- Low

         Feeding- Dry Commercial Foods OK

         Feeding Frequency- 1 - 3x per day

         Live Food - Very Beneficial

         Size- 4 - 5.5 inches


Community Fish- Yes

Behavior-Peaceful but active

Jumpers- Not generally

Tank covered- Yes

Substrate- Minimal

Live plants- Yes

Gestation- 30-40 days

Size Broods- 10- 40+ young

Predate young- No

Raise young separately- Yes

Fry Raising - Easy

1-5 Level of Difficulty, (1 easiest) - 3


    Most monty males will develop swords that are at least 1.5
    times their body length. Aware of this badge of distinction,
    they are constantly showing off to one another, and a ranking
    order does establish itself. However, the males never seem
    to damage one another's fins, though they will chase one
    another around.
      Occasionally males will appear with exceptionally long
    swords, and many monties seem to continue to grow
    their sword throughout their lifetimes, so that a fish
    with a very long sword is often a very old fish.
    This fish is nearly 6 inches long, but its body is less
    than 2 inches long.

     Similar to the way in which the Poecilia velifera is not a pet shop molly,
     the Xiphophorus montezumae is not just another swordtail. There is a reason
     why the X. mayae or X. helleri have been nearly always available, but the
     "montys" have only been available about a third of the time. Smaller brood
     sizes, the need for long term consistent water quality and clean conditions,
     combined with a healthy diet may account for why they are not more
     frequently seen.

     By far these Tamosopos are the most dramatic swordtail, with tuxedo black
     markings and extremely long sword, a sword that is routinely 1.5 times its
     body length.

     Also see the basic Care guide for this fish HERE.

     When first obtained about 6 years ago,  I
     was told this line produced males with
     red stripes, which is one color rarely
     seen on a monty. It is true, and the
     orange/red markings can be seen on this
     male. However, I have not yet attempted
     to select breeders for the red color.

          The montezumae is not the biggest swordtail. Stories of 9 inch montezumaes in the wild exist, but in the aquarium,
          efforts by many to increase their size - from nose tip to sword tip - has not produced individuals larger than 5.5 inches.
          The X. helleri Rio Otapa will produce males that have reached 6.25 inches here, and the X. mayae has produced
          occasional males that have reached 6 inches. See How big will these fish get, for info on efforts to reproduce the larger
          fish claimed to be seen in the wild.


         When kept in conditions discussed in this essay, they are generally a hardy fish, tolerating temps up to roughly
         80 degrees, and doing best at 74-78 degrees. However, the areas where this fish needs special attention are often
         overlooked. The result is they are rarely seen or offered. Though over 300 have been shipped since Select Aquatics
         began, they can still be difficult to find, and stories of unhealthy fish or early maturing males being sent out to customers
         are complaints that have been received. The result is that this robust line has not been readily available, and many
         tanks have been set up here to get these back out into the hobby.

    Trios can be bred in 10 gallon tanks, and for breeding it is best to put a single
     male with 2 or 3 females. With a colony of multiple mixed sex fish, a tank of at
     least 29 gallons should be used. Though the larger males will assert dominance 
     and establish an order of heirarchy, they never seem to cause any damage to one 
-    another, though there can be some chasing.

     Unlike other swords, they are not fry eaters, and most fry do well when born into
     a tank of adults, but they should be caught and separated to a 10 gallon tank to
     grow out and have better access to food. Experience here has shown that batches 
     of fry do not do well when kept and raised in net breeders. For some reason, up to
     half of batches can be lost when confined to a net breeder. Sometimes a "whirling" 
     condition will overcome their swimming when in a closely confined net or plastic 
     breeder, and they will then start dying shortly thereafter. It appears to be a disease,  
     and I have seen it in two lines I have received over the past 10 years. This line here 
     has been here since 2010. We no longer use net breeders, and that condition has
     not been seen here for at least 4 years.

     They will drop 10-30 young after a gestation of roughly 30 days, depending on
     temperature. As they mature, they do produce occasional early maturing males,
     and these should be culled to maintain the size and robust health of the line.
     Similar to other swords, secondary sexual characteristics begin to present
     themselves at 4-5 months, and first groups of fry are produced 7-10 months.
     Later maturing males should be used as breeders, as they will be your larger
     individuals, and they may take 7-9 months before being ready to breed. It is
     thought that some of the rumors of their taking up to 18 months- 2 years to sex
     out may be connected to the length of their swords, as they seem to continue to
     grow throughout their lives. Older males dragging around swords over twice their
     body length are not uncommon. But like all swordtails, breeding will begin as
     soon as the gonopodium is present, and sword length does not matter.

    Kept in the standard fashion described
    throughout the site, the young
    are raised in 30 gallon grow out
    tanks with a diet heavy in BBS,
    red, black and white worms, and
    a flake diet rich in both a
    vegetable component and quality
    protein ingredients.

    Though they are very good about not
    eating their fry, all fry should
    be removed and placed into a smaller
    tank to be raised separately. However,
    young do best when they are not
    confined to a net breeder, but allowed
    to grow out in a moderately planted tank
    with minimal substrate, healthy aeration,
    and effective filtration.


                                                                 An Issue with raising Their Fry

     Many of us will put a gravid female into a net breeder to drop her fry, so that few are lost. The montezumaes are very good
     about not eating their fry when they are well fed. When first obtained here, females dropped in net breeders, and the first
     few batches would sometimes develop a "whirling" behavior, and they would die shortly afterwards. This was occurring
     to nearly 50% of the fry in some batches.

     I treated with medications, etc., to no result, but began having females drop in moderately planted 10 gallon tanks, instead
     of the confined breeders. or just pulling fry from the adult tanks as I saw them. Today many hundreds have been bred and it
     has not happened since. However, over the past 6 years, 2 customers let me know that they experienced this as well. Both 
     were using smaller breeders as well. I cannot identify what this is, but using small breeders for this fish can sometimes have
     a negative effect on the new fry.


     A 40 or 55 gallon tank are ideal for them, and a group of fully sworded males
     with their tall speckled dorsals makes any effort to provide what they need worth
     the effort. Generally they are easy to keep and can be fairly prolific. New fry
     should be routinely raised up separate from the adults, and when kept in a community
     tank, thought should be given to the possibility of their being nipped by other fish.
     The monties are not aggressive to other fish

     This is a group of 5 month old generally unsexed fish. Females can often be
     identified by a darkening gravid spot at about this age. They are a sleek, shiny,
     golden fish that is unlike any other swordtail, and young can be identified as
     montezumaes easily.


          The issues with the montezumaes comes down to water quality and feeding. In a tank with a bottom of accumulating
          mulm, the fish may produce at a rate that will keep the line going, but losses before reaching adulthood will occur.
          The monties require moderate aeration, good filtration and a varied diet of dry foods, baby brine shrimp for new fry,
          and various frozen and live foods to ensure better health, such as frozen adult brine shrimp, bloodworms, etc.
          Live feedings of blackworms, chopped redworms or white worms are taken eagerly.

          The Montezumae tanks are set up here in the manner described throughout this site, for more info, see "A
          cleaner Approach to Fishkeeping". All tanks are bare bottom with a single layer of 1/4" pea gravel over 1/3 - 1/2 of
          the tank bottom. A filter that removes debris from the aquarium (Not sponge or undergravel filters) is used and weekly
          water changes of 50%+ are done. Two changes of 25% per week is even better for  the stability of the tanks,
          and the overall health of the fish. However, 50% per week will keep them in good shape.


          In 20 years of keeping this fish they have been particularly disease resistant. I have never had a case of
          ich or fin rot with this fish. However, they do seem to be prone to "livebearer disease" when the parasitic
          organism is present. They can be cured with the use of Levamisole. This condition is evidenced by a thinning
          down and eventual wasting away of the fish. Within a couple weeks it then results in the loss of the fish.

          The Xiphophorus montezumae is easily the most elegant and regal swordtail that one can keep, and this
          population is the largest and most colorful, with the longest sword of any swordtail. Please consider keeping
          this fish, as it would be a tremendous shame to lose this fish from the hobby!





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