Select Aquatics of Erie, CO.

    Back to Fishkeeping Tips 11 "Breeding"


                           Breeding the Livebearers Found at This Site
              (revised Jan. 2016)

                  Water movement, aeration, water changes, not overcrowding and abundant quality food ensure your best
                  chance of success. Feeding live and frozen foods, earthworms or a quality earthworm flake in particular,
                  seems to increase both the size and health of the broods. Baby brine shrimp is good, but many adults cannot
                  feed completely on it, so I do not depend on it for adult fish. Daphnia is excellent, adult Brine shrimp (frozen
                  works well), white worms, etc. are all good. Feed at least twice per day, ensuring the tank stays reasonably
                  clean. Mulm must be removed when it accumulates- heavy filtration or water changes do not eliminate its
                  negative effect on the fish- it is not "inert". Inedible, decaying organic material is never good for the fish or
                  the fry. Not only do these practices lead to healthier fry, but frequent feeding helps ensure that new fry are
                  not immediately gobbled up if a female drops before you are able to remove her. A good diet before a drop
                  helps guarantee robust, vigorous fry. A poor diet can lead to fry that are born dead, or that die shortly after
                  birth, or that develop air bladder problems during their initial development. (“Belly sliders”)

                 Breeding traps for swords just don’t work. The traps are too small, and the female is often distressed
                 by her lack of movement (particularly when Java moss is also added so that babies have a place to hide)
                 that she may drop early, releasing her fry in an undeveloped condition, where only a few, if any survive.
                 Or she will become unable to drop until she becomes huge, and then she dies- before releasing the young.
                 A female that is gravid (she is large, and her black “gravid spot” just behind the belly has become dark)
                 needs to be moved into a small tank of her own with some aeration, filled with fine leaved plants, but not 
                 so much that she cannot swim around. The tank must be at the temperature of her original tank, 
                 and filtration (possibly through heavy daily water changes) is essential. Dirty water compromises 
                 the survival of the new fry. Gestation for most swords, mollies, platies and guppies is about 25-40 days,
                 depending on temperature.

                One solution that does work has been to create breeders from plastic "shoebox" style containers or larger 
                plastic storage boxes that are small enough to sit within a larger aquarium. The sides and bottom are cut
                out, then covered with fine nylon mesh, glued in with a waterproof glue. (see pic on left of Fishkeeping Tips 11 
                breeder page). When those are used, be sure to glue a couple marbles to the side of the breeder that will 
                face against the aquarium glass, to prevent smaller fish in the tank from becoming trapped, which can  
                cause a loss of fish.

                New fry should be fed newly hatched baby brine shrimp, but can be raised on an artemia substitute or
                other fine dry foods. For swordtails, guppies, mollies and platies, fry can be raised slightly warmer
                (78-80 degrees) to assist their growth. Goodeid fry should be raised at the cooler temps- 72-75 that the
                adults prefer) Fry also need to be fed 2-4 times per day at first with daily water changes of 50%, unless
                in a container with adequate filtration, or in a breeder that sits within a larger body of water. Leave some
                Java moss in with the fry to assist water quality, but not so much that you cannot see all of the fry easily to
                monitor their condition, or that cause decaying food to become trapped. Add aeration with at least a mild
                air flow from an airstone if possible. Baby brine shrimp and/or the high protein fry foods foul the water
                quickly, and go bad within just a few hours. A quick ammonia spike will kill new fry fairly quickly. A rule
                that I have discovered over many years, and that seemingly makes little sense, is that fish that cannot be
                seen and monitored inevitably suffer losses, whereas fish that can be watched and kept an eye on will do
                better. I know it doesn't make sense, but we all tend to neglect the tanks, just enough, that we don't follow

               After 3-6 weeks (depending on species) the fry can be released in with the adults. Feed the adults well,
               then release just a couple new fry into the tank, watching to see if they get chased such that they could be
               eaten. All adults will chase a new fish to check it out, but when they determine the other fish is too large
               to eat, they will back off. If the adults don't back off, rescue the released young and wait another week.

               The Goodeids- These fish can be the easiest to breed, but building up their numbers can be a long process
               interrupted by long periods of fish not becoming gravid. Some species will take a break from breeding from
               approximately mid September to April, their gestation is around 60 days, and a young female having her first 
               batch of fry may only drop 4 or 5 babies. Though the fry are large, having been nourished by the mother in
               utero similar to mammals, they are still often eaten by the adults. The hiatus some species will take from
               breeding over the winter may be triggered by exposure to natural day-night seasonal light cycles, and
               friends with fishrooms without windows, where they can control the light periods, tell me they don't
               experience those seasonal breeding fluctuations.

               Many goodeids do not generally eat their young, but the gravid females of some species do not do well
               when moved to drop their fry. Occasionally after being moved a female will simply drop her brood stillborn.
               I have found that the home-made breeders mentioned earlier will work when hung in the tank where the
               female resides otherwise. Often I simply watch gravid females, then I will save as many new fry as I can to 
               raise them separately until large enough to fare on their own.

               With Z. tequila the females can be moved reasonably well, but definitely do best in their own 5 or 10 gallon
               to have their fry with lots of Java moss (or fern). Moving to an unfiltered (but with plants) 2 gallon container
               or a breeder can result in the death of the gravid female. Other adults will eat the fry, and when allowed to
               community breed (where young are simply not removed, with hope that the population will increase over
               time) my experience has been that their numbers will generally decline over time, rather than increase in
               Characodon lateralis will increase in numbers when kept simply as a community, but will be occasionally
               eaten. Their broods are often only 5-10 young, and the new fry generally do not fare well when left to grow
               out in an adult tank. However, the females tolerate being moved, and the young do well when raised up

               The Goodeids will grow out fairly evenly when well fed, but that is not the case with the Swordtails.
               Most swordtail species have an anomoly where occasional males are born that reach sexual maturity far
               earlier than their siblings, an evolutionary tactic that allows some males to gain access sexually to the
               females before the other males in the tank, producing other early maturing males in the process. The
               problem is that these males will be dramatically undersized, often with poor color and traits that are
               not positive for the line. The only solution, until the line is stabilized (in that the appearance of early
               maturing males is rare or nearly nonexistent), is to raise the sexes separately, then select for the 
               largest, most robust fish, culling the early maturing males.

               The Swordtails- These cannot all be considered as breeding the same way, or all given the the same
               surroundings and treated the same way to achieve the best results. Some breed more readily than others,
               and batch sizes can vary from 10 to 40, depending on species. Here is what we have found here, and I will
               start from the easiest and most prolific.

               Xiphophorus mayae- A sword that is generally shyer and more "wild" in behavior, they show little aggression
               or dominance issues with one another. Males can be kept together with a grup of females, and in a well
               planted tank with adequate feeding they will generally not eat their fry. Fry should be removed when seen
               and raised up separately so they will have easy access to food and experience maximum growth. They are
               considered the largest swordtail.

               Xiphophorus alvarezi, Gold - These are less prolific than the wilds in that they breed slightly less often,
               and the batches can produce fry with varying amounts of red markings. These generally do not seem to eat their
               fry, but because some batches from some females can contain fry that are albino or weaker, I generally remove
               the females to their own tank to have their fry, and then raise the fry separately on BBS. Interestingly,
               many adults tend to get huskier and longer than the wild alvarezis they came from, but rarely surpass 5 inches.

               Xiphophorus helleri, Rio Otapa- A very large swrd, the larger dominant males can be aggressive to smaller male
               tankmates. These get very large, and a big female can easily produce 50-60 fry. They are also fairly prolific.
               They may eat their fry, but so many are produced in a tank of adults that the tank will quickly "crash" if the
               fry are not removed due to an overload of organic waste. But there is a problem. At first many keeping this fish
               had sex ratio issues, where entire batches that grew out were all male or female. After years of experimenting
               with this, I have reached 50/50 sex ratios by feeding new young finely powdered food and live baby brine shrimp.
               Feeding a crushed flake will not do the trick. these also take a long time to sex out. Where the alvarezi may
               begin to show secondary sexual characteristics at 4 months, the Rio Otapas, like the montezumaes, may not begin
               to sex out until 6 months or older. The other issue with these is that unless you have 100 gallon tanks just for
               Otapa fry, you will want to watch your tank density as they grow out. Too many fish will result in their being
               stunted, and these will get to be especially large and colorful.

               Xiphophorus montezumae- These are a very different swordtail. When breeding for numbers, the best way is to breed
               them in trios in 10 or 15 gallon tanks with moderate to heavy planting, frequent feeding and water changes. These
               do not eat their fry. they will breed slightly less frequently, and the batches are generally 10-40 fry. I have
               found that the young do not do as well as other swords when it comes to being raised up in net breeders.
               Mortality is higher and they will often develop afflictions when raised in a confined space. So with the monties
               I will either remove the female to drop fry in another tank and raise the fry separately, or let the female drop
               her fry (As they do not eat them), then remove them as soon as they are seen. these also grow slowly, and may
               take 8 months to a year to fully sex out and produce fry.

               Early Maturing Males

               All of the sword species, and some molly species will produce Early Maturing Males, and these must be removed as
               soon as they are seen. Early maturing males are an adaption made by these species, where a percentage of males
               will sexually mature earlier than their brothers, and do not use a courtship behavior to mate. The result is a
               smaller size, but you are able to get your genes out there before anyone else. All of the Xiphophorus swords I
               have worked with have this, and breeding the trait out of the line can be done, but they must be removed over
               many generations for the trait to disappear.






        These are Early Maturing Males of the Xiphophorus alvarezi. They
        are perfectly healthy, and have fully sexed out with a full sword,
        yet their body length is under an inch long! Allowing these to
        propagate in your colony tank of alvarezi will cause your line to
        deteriorate quickly. The fish will reduce in size, and the EM 
        males are rarely as nicely colored as full sized fish.



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