Select Aquatics of Erie, CO

                         Keeping the Yucatan Sailfin Molly

                                             Poecilia velifera



          Basic Stats:

      Size tank- 29 gallons or larger

         pH - 7.6 - 8.4

         Hardness- Moderately hard +

         Filtration- Heavy filtration

         Aeration- Moderate to heavy

         Water movement- Yes

         Nitrate tolerance- Low

         Feeding- 80% vegetable based, 20% protein

         Feeding Frequency- 2-5x+ per day

         Live Food - Not essential

         Size- 4-5 inches+


Community Fish- Yes

Behavior-Peaceful but active

Jumpers- No

Tank covered- Yes

Substrate- Minimal

Live plants- Yes

Gestation- 30-40 days

Size Broods- 10- 30+ young

Predate young- No

Raise young separately- Yes

Fry Raising - Easy

1-5 Level of Difficulty, (1 easiest) - 2



     Everyone would like to keep the Poeclia velifera, the Giant Sailfin Molly, particularly
     the well known population from the Yucatan Peninsula. It is the iconic Livebearer,
     the symbol of the American Livebearer Association, with a huge fan dorsal covered 
     with fine, bright and crisp blue, red and orange markings over its body. It is not
     easy to find in the hobby, and for those able to obtain it, they soon find out that this
     is no pet shop molly.

     Nothing else looks like this fish, and a large male doing his high energy display for
     a female, opening up that huge dorsal, where the first dorsal spine comes all of the
     way forward so that is points straight ahead, will take your breath away. They are 
     are also fairly prolific, so that when you get their care dialed in, they generally do
     very well. They are also well behaved, non aggressive to one another and other
     species, and generally do not eat their fry.

     Also see the basic Care guide for this fish HERE.

     A young male displaying. They will often
     display after being fed and following water
     changes. Some males display more than
     others, this guy will show off 4-5 times a

          Large bull males will sometimes reach 5.5 inches, and it is not necessary to grow these out in outdoor ponds or large
          tanks for them to develop their sail dorsal, as was once believed. A few can be kept fairly comfortably in a 40 gallon tank, 
          most are kept in 55s here.


      Although the pic at left is of poor quality, This is the biggest male I have had here
     so far, and is about 5 inches in this picture, well on his way to being a 5.5 - 6 inch
     fish. Shortly after this pic was taken, this male developed a large tumor on his side
     and had to be culled. Today I have a number of late maturing males growing out,
     and hope to have others at least this large in the future!


          Nor do they require salt in their water. This line has never been kept with salt, and does fine without it. However,
          particularly when I have acclimated them here, I will use salt to ease their transition when coming from another
          set of water qualities. They respond to salt well, and it does come in handy whenever they may not look their best.
          A quick medicinal dose will always perk them up. (1 tablespoon per every 5 gallons of water).

          Continued selective breeding by breeder friends has kept this line large, with frequent, spectacularly colored,
          large males being produced.

          However, this fish has a number of requirements that must be provided for them to do well. I will carefully explain exactly
          how we keep them here so that if you wish to keep them they should be at their best for you. Their needs come down
          to a few specific physical characteristics that need to be understood, and these issues dictate the care they require.

     Anyone can keep this fish, but it is not a "beginner Fish". Their care is not
     difficult to provide, but some may decide this is not the fish for them.
     It is currently kept by few fishkeepers, so hopefully with the information here,
     more can keep this fish successfully and bring them  back into the hobby.
     I understand that this information is not  easy to find, so I will do my best to
     describe their care requirements here.  

     These are not a difficult fish to keep properly, you simply have to set out to create a
     tank that meets their needs. Nor are they fragile in any way - when kept correctly
     they are an active, hardy, prolific fish. The issue, as I will address, involves
     appropriate filtration, and their need to be fed more than once per day.

   A group of adolescent velifera just sexing out.


          Like any fish with special needs, until you get their care dialed in, these should be kept in species only tanks, where except
          for a pleco or catfish, this large and prolific fish should have the tank to themselves.

          Before I go further, some customers have asked about putting these into a standard, reasonably well kept community tank,
          and how well will they do? Assuming we are talking about a moderate stocking level with 1x-2x feedings per day of a quality
          vegetable based dry food, with good filtration and aeration, and a pH of about 8.0, they should do OK for a while, and may
          even reach adulthood when kept in reasonably clean conditions. But if you want the glory these fish are capable of,
          it is best to start off giving them the conditions they require to do their best. Today, these have become a rare fish in the
          hobby, yet are possibly he most spectacular fish you can keep. Learn to keep them so they do well, and here will always
          be hobbyists looking for them!

    Their tanks are set up as described throughout this site, bare bottom with a thin
     layer of pea gravel over a minimum of 1/3 - 1/2 of the tank bottom. However, they
     do need to be at a pH of about 8.0, so instead of pea gravel here, about 1/2 of
     the tank bottom is covered with crushed oyster shell to bring up the hardness
     and pH (My pH is about 7.4). They are also a slightly warmer water fish, and do
     best here at 77-80 degrees, though some keep these routinely as warm as 82-83
     degrees. To keep oxygen and filtration as high as possible, I do not go higher
     than 78/79 degrees. (Cooler water holds more oxygen)

     The problem with this fish, the reason it is not more widely kept, is that it has
     two aspects to its care required for its survival, and they conflict with one another.
     Before you get this fish, you must provide a setup that solves this problem, and
     getting on top of it will guarantee that they will do well for you.

     Box filers are used as the primary source
     of filtration as they are very effective at
     removing debris and mulm. How dirty
     they are can be seen immediately.

          Here is the issue:

          This fish is a "grazer", eating fairly constantly in the wild. While preferring a vegetable heavy diet, they possess a
          relatively short digestive tract. Normally, an animal with a vegetarian diet has a longer digestive system as plant material
          is more difficult to process and takes longer to digest. With a short digestive tract, they then digest what they take in
          inefficiently, releasing more waste than most fish we keep. Because of this, they must be fed smaller amounts
          throughout the day. With a schedule where you must be gone during the day, they will survive with a feeding in the AM, and
          then 2 more times before nightfall. Ideally, the tank should be located where they can be fed a small amount each time
          someone walks past. Here, they are fed 5-6xs per day. And with each feeding they act as if they are starving, yet may be
          stuffing themselves with bodies already well rounded! Because I am in the fishroom all day, I am able to feed each time I
          walk past the tank, but obtaining a quality automatic feeder would be a consideration. 

          The conflicting issue is that they are also somewhat nitrate intolerant, and their health will decline when water quality is
          inconsistent or is allowed to deteriorate. And of course, with all that feeding, water quality will deteriorate quickly.
          This is not a deal breaker, appropriate filtration and water changes will take care of that, but you need to first set up a
          tank of at least 29 gallons with heavy filtration and routine access to at least 2x per week water changes of at least 30%
          each time to maintain them, depending on the number of fish in the aquarium. The more fish, the greater the need for
          extra filtration. Full sized adult fish will need to be moved to at least a 40 gallon aquarium.

          Here, two breeder groups are maintained, about 25 of the largest fish are in a 100 gallon tank, and a second group of
          10-12 large, but not the biggest fish, are in another 55 gallon. Early maturing males are culled. The tanks are filtered
          with 3 and 4 box filters, and each tank also has a 250 HOT Magnum HOB filter with the micro cartridge to keep water
          quality up. An automatic water change system changes the water 15% per day. You should be able to maintain them with
          weekly 50-75% water changes.  If stocking levels get high, occasionally doing a 20-30% change whenever the water
          appears the least bit cloudy is advised. You must provide filtration that removes the majority of waste from the water.
          Because they are nitrate intolerant, a sponge filter that is cleaned regularly (weekly) can be used in conjunction
          with box or HOB filters, but are never to be used as the sole source of filtration (as any any sponge based filter leaves
          the mulm and decaying matter in the tank).

          Obviously, you will not need the canister Hang On Back filter with a few smaller fish in a 40 gallon aquarium, but you will
          need that extra filtration as they each reach 3.5 inches plus. Through observation you can come to understand what they look
          like at their healthiest, and add filtration or make changes to the water quality as necessary.

          The box filters provide robust aeration, and the velifera do not seem to bother the live Java and Bolbitis ferns provided in
          the tanks. They do not eat their fry, which hide in the plants and are easily caught and moved to grow out tanks where
          they are fed BBS, and 3-4xs per day feedings of a fortified vegetable flake.

          Though fed a vegetable based dry flake throughout the day, they must also be fed one feeding a day of a higher protein food.
          Here we feed a carnivorous flake, or frozen bloodworms, white worms or chopped earthworms. Frozen Brine shrimp is also
          excellent for them.


     This is group of fry being grown out in a homemade net type breeder. They
     need to be grown out with frequent feedings to reach adulthood at maximum
     growth. These do not sex out until they are fairly large - 2-3 inches, and
     poor care of fry will lead to undersized fish that will sex out even later.
     Because they are so food oriented, the young are kept in breeders
     until they approach 3/4ths of an inch (4-6 weeks). These are about to
     be released into the 40 gallon tank used to grow out young fish. When a
     group of 6 fish are purchased, they will be between this size and
     about 1.25 inches.


          Raising the fry is not entirely what you would expect. Fortunately, when well fed they generally do not bother their fry,
          born only slightly larger than a swordtail or guppy fry. It is best to put them into a net breeder, and for the first month or
          so of growth, there are no real signs that they will grow into the large 4-5 inch fish we are hoping for. The growth is
          fairly slow, and they are only about the size of a swordtail or platy fry until about 5-6 weeks. At this point, with frequent
          frequent feedings and good water quality, their growth begins to take off. 

     These sex out differently than the swordtails or mollies. There is very little to
     indicate who is going to be a male or a female until they have reached a good
     1.5-2 inches. Some late maturing males (which are the ones you want to use as
     breeders, as they will be the biggest fish) may not show secondary sexual
     characteristics until they are even larger. The top fish in this photo is just
     starting to show the thickening of the gonopodium, and the dorsal has just begun
     to show development of the fine markings that define the big sailfin dorsal.
     These will also produce broods that are female heavy. The ratio still provides
     frequent males, but the ratio here has been roughly 4-1 females to males in
     the conditions (temp and pH) they are kept here.


          At about 3/4 inch I move the fry into a 40 breeder tank, where their growth is encouraged, after they are old enough
          to be feeding confidently and swimming throughout the tank. All look, at this point, like smaller females.  It will take
          a good 5-6 months before you will start to see firm signs of males beginning to sex out. The problem is that those
          sexing out first are generally the "early maturing males" that will sex out at a very small size, and you want to
          separate those, so they do not breed with your stock, or the line will diminish in size. Eventually, the big bull males
          will begin to sex out, and those are the fish you want to use as breeders. Keep in mind when raising these fry, if 
          possible, to feed small amounts of food throughout the day. Here they get BBS once a day, and  numerous
          smaller feedings of a spirulina based flake.

     Here are 3 fish with a smaller male that is more developed than the male above,
     the young male on the left. Already the less mature male is larger than the fish
     that is that has sexed out further. The more developed fish already has a
     dorsal that has gotten too large to carry erect unless he is trying to draw
     attention to himself. The neon blue color is beginning to come out, and you can see
     the black outlining starting on the tail. These males are likely the same age, but
     the larger fish is later maturing. The more developed fish is still a nice male.
     I do not consider this to be an early maturing fish, I have seen fish develop
     gonopodiums here at just 1-1.5 inches, and those are culled. This developing male
     currently is about 2.5-3 inches, and will likely top out at about 3.5 - 4 inches.
     The larger, later maturing fish may eventually reach 5 inches. The top fish
     appears to be a clear female.

     This male has his adult color, and is about 4.5 inches long. You can see the
     incredible color that this fish possesses. Under a pen flashlight the spangles are 
     a bright green/blue, and this line produces many males with a canary yellow
     undercast. When any of these males are in full display it really takes your breath
     away! This male will often display after being fed, and after water changes.


          Until the males begin to develop color and that big sailfin, they are fairly indistinct, chunky silverish-white fish. Overall,
          it will take a male about 8-12 months to become full sized, and it will take 5-6 months before they can be sexed. Once
          secondary sexual characteristics start to develop, the males will grow quickly, with the sailfin growing daily. At this
          point the sexes should be separated, so that your largest fish of those growing out are bred toward the next generation.

          For the experienced fishkeeper looking for a modest challenge with a big payoff, and a show tank that people will not  
          be able to look away from, this may be the fish for you! Though water quality can be tricky to get dialed in, once that is 
          established, they are a very well behaved, peaceful and large colorful fish that do not eat their fry.


     The best way to obtain these is as younger fish, in a 2-4 month old group that are
     about 3/4 - 1 inch in size, as they will be least expensive to ship and will survive
     shipping with the fewest losses. Have a 30 or 40 gallon, lightly planted tank with live
     plants (so you can keep an eye on them, and to help maintain water quality) set
     up following the guidelines above - pH 8.0, 78 degrees, single layer of gravel over
     1/2 of tank bottom, generous filtration and oxygenation, species only, moderate lighting,
     frequent feeding, and the ability to do quick, spot water changes when necessary, with
     routine weekly or twice weekly water changes of at least 50% weekly.

                       How often do the males flare, and can you encourage them show off?

              Here there are two tanks of adult fish, a 55 and a 100. The 55 has approximately 5 males, two that are full
                  adults, and 8-9 females. The dominant male will flare 4-5 times a day with casual observation, primarily after
                  feedings and water changes (and that is when I am most often there to observe them). As the males mature, 
                  and are in the same tank together with females, the amount of flaring is frequent enough that it can be seen
                  a few times per day.

                  The 100 gallon has a big bull male of about 5 inches with about 15 larger females. He rarely flares, and in fact
                  I have only seem him flare on a couple occasions. Yet, that tank produces many fry consistently. My thinking is
                  that the flaring is for both the females and competing males, and having both together in the same tank will
                  increase the amount of flaring going on.

                  They can also be encouraged to flare by separating the males from the females for a short period (a day or two),
                  and reintroduce them followed by a water change and/or feeding.




                  Currently breeder groups are producing fry that are sold at 2-3 months. Over time, sexed young adults will be
                  offered as they become available. Availability of fry groups and sexed adults will be posted at the homepage.

                  If you have any further questions or concerns, or want to make a comment on anything I have written at this
                  site, I would like to hear from you- just email me at . Thank you!





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