Swordtail Fish are one of the most bred freshwater fish in the world. From genetic studies in melanoma research to easy breeding by absolute beginners, they have been extensively propagated worldwide for centuries.
Their sheer diversity in color, easy breeding, and sociability make them a conspicuous addition to many aquariums.
This playful and dynamic fish requires as natural a habitat as possible to prosper, but have also been known to pack up and escape tanks if they think greener pastures can be found elsewhere!
Here we examine the best practices and some common pitfalls on keeping these beautiful, highly social creatures whether you are an aspiring hobbyist, commercial breeder, or seasoned veteran.
Species Overview
There are over 28 individual species in the genus Xiphophorus all of which are native to Central America. This includes swordtail fish and their near brethren the platyfish.
Many of them include hybridization among the genera and have been identified as species in their own right. These should however not be confused with their Old World cousins from the Family Aplocheilidae, like the lyretail and the panchax.
| Category | Rating |
| Life Span | 3-5 Years |
| Family | Poeciliidae |
| Color Variety | Various |
| Care Level | Easy |
| Compatability | Peaceful with Many Types of Fish |
| Food and Diet | Omnivore |
| Temperament | Docile |
| Tank Size (Min.) | 15 Gallons |
| Tank Setup | Rocks and Plants in Freshwater |
| Size | 5.5-6.5 inches |
Green swordtails (Xiphophorus helleri), southern platyfish (Xiphophorus maculatus), and variable platyfish (Xiphophorus variatus) are among the most commonly kept varieties.
These are readily available from reputable breeders, local and online pet stores as captive-bred specimens. They are highly social fish and cohabitate easily with most other non-predators.
Lifespan
While some swordtail fish owners have reportedly kept their top breeders for nearly a decade, the average lifespan is about four years in captivity.
Getting your fish from a reputable breeder will ensure that your swordtails are of the highest pedigree, are brilliantly colored, and live as long as possible with the correct care.
Appearance
Due to their wide proliferation and cross-breeding, swordtails can be found in almost every color combination imaginable.
While orange, black or green with brown or red lateral stripes are the most common colors, specimens have also been found painted with everything from neon to orange and tinfoil silver.
Beyond color, there are also variations of pattern with more aggressive stripes, spots, calico splotches, and even complete albinos.
The latter should not be confused with the Albino Koi Kohaku Swordtail which is a rare and highly-valued bright orange and silver-colored variant whereas the former refers to a general lack of pigmentation.
Their bodies are stereotypical of many fish with a streamlined body and wide tail fin for minimum drag and maximum propulsion. This design which took human engineers millennia to replicate was perfected by nature long ago.
The most defining feature of the Swordtail Fish is the male’s caudal fin. Like other attributes, breeders have managed to select those with the longest tails for maximum flash. The result has been striking with some caudal fins exceeding the length of the rest of the fish.
Size
Although females lack the namesake sword-like tail they still tend to be about 10% larger than their male counterparts even with the most exaggerated bred-in attributes. Overall it is considered a medium-sized, tropical, freshwater fish.
Swordtail Fish Care
Swordtail Fish are amongst the easiest domestic fish to keep and make trouble-free housemates. Generally, they are resistant to most diseases and make themselves home in a variety of water conditions.
The most important thing is that they have a large enough space to live, play, mate, and explore.
With the correct balance of aquarium size relative to the number of fish, proper feeding, and regular water and tank maintenance even the beginner can prove their mettle with a proud school of swordtails.
Tank Size
Anything smaller than 15 gallons will sadden a single Swordtail Fish – they need room to play.
When breeding them it is essential that you plan for enough space to accommodate your eventual school; just plan a contingency of 25% more capacity than you originally expected.
This will allow you to fill the tank with rocks, vegetation, and other curiae and still leave them sufficient space to explore.
You will also want to have separate holding spaces for your newborns. As with many fish, they are liable to eat some or all of the fry. Alternatively, you can choose to use a separate breeding tank for juveniles if that method is preferred.
Water Parameters
Normally Swordtail Fish make their homes in a wide variety of streams, rivers, estuaries, and creeks throughout the tropics. As with many domesticated pets, you are trying your best to mimic their natural habitat.
They are highly resilient and adaptable to a wide range of water PH balances, temperatures, and degrees of salinity. Ideally, you want to aim for a tank near 80F, with just slightly alkaline, salt-free water (PH near 7.7) to make these freshwater river fish feel at home.
What To Put In Their Tank?
Again we are trying to mimic conditions of the streams, rivers, and creeks in the tropics of Central America they call home.
Beyond abundant plants, rocks, and hiding places to explore it is useful to also consider a good power-head. This helps mimic natural currents, regularly renew oxygen in the water, and maintain good circulation.
When it comes to plants, live plants will always do more to enhance environmental conditions. Beginners might be tempted to add decor or personal items to the tank but be careful.
If the objects for your tank are plastic or metal it is possible for hormones, toxins, or even minute polymers to harm your guests; unfortunately, many newbies make this innocent error.
So, stick with natural materials for your substrate, decor, and habitat. And once your visitors have arrived, also be certain to affix a good lid. Swordtail Fish are prolific jumpers and liable to make a run if given the chance; indeed this sword might prove mightier than their pen.
Common Diseases
Like similar freshwater species, Swordtail Fish have excellent immune systems and do not suffer from many endemic illnesses.
The most problematic illnesses they suffer come from fungal and viral sources. While having a clean, healthy tank is your best bet at prevention if they do get sick, most health issues can be controlled through prudent quarantine of sick animals and timely use of therapeutic medications.
What do Swordtail Fish Eat?
They will eat almost anything, but please don’t start dropping popcorn into their tank as others have done for show, as a trick, or for a treat.
There are few of these snacks in the Central American tropics to be found and if you feed your pets highly complex, processed foods it is liable to make these omnivores quite ill.
Better to stick with what they can find at home: aquatic insects, plants, and micro-organisms.
While you can share some of your snacks with them as a treat (zucchini, cucumber, peas, cabbage, or ironically enough – unsalted seaweed) their main diet should include a protein pellet or flaked complete fish feed with supplemental minerals and vitamins.
This along with the aforementioned veggie treats and pet store-bought aquatic snacks (crustaceans, larvae, and worms) can formulate an overall balanced diet to foster optimum health and happiness.
Behavior & Temperament
While you are not likely to be able to train them to jump through rings of fire, Swordtail Fish are highly active, yet docile fish making them an attractive pet.
Normally, they prefer to spend much of their day between the surface-to-mid section of any body of water feeding there opportunistically throughout the day on prime, small meals.
These typical behaviors are well demonstrated in this wild footage captured by a casual observer.
At home, you can expect the same calm but inquisitive behavior; though there is one exception: the rutting season.
Alright so they don’t charge like moose or caterwaul like an unhappy kitty in estrus but the male Swordtail Fish is a force to be reckoned with when it comes to passing on its genes. They will compete, beat or eat any unwelcome competitors for a mate.
This is the only time there is a concerted aggressive behavior from these little creatures, when there is mating competition or a shortage of food.
It can be alleviated by regular feeding, ensuring that a high ratio of females to males in your tank, and controlled segregation of individuals for selective breeding.
Normally through regular observation and getting to know your mates will you also pick up on the subtler behaviors seen in this species.
If they are constantly fighting, time to look at the dating pool. If they are sluggish and not exploratory, time to check their physical health and the overall cleanliness of their home.
Swordtail Fish Tank Mates
If you are building a community tank, Swordtail Fish are amongst the noblest of potential citizens. They get along well with other non-aggressive, similarly-sized fish.
Many people opt for numerous kinds of other small decorative fishes to customize their underwater kaleidoscope.
While the competition for similar foods and spatial spats can break at any time in a community tank, most of the time Swordtail Fish will school and then segregate solitarily as they would in nature.
In light of their good neighborly conduct, there are many compatible matches building your freshwater utopia. The most common (unrelated) companions are angelfish, barbs, and tetras (such as the Black Skirt Tetra).
Be sure to also consider adding bottom-feeders like cichlids and plecos, such as the Clown Pleco, as companions. These come with the added benefit of social distancing since neither they nor the Swordtail Fish will be competing for this aquarium space.
Breeding
Some fish are very difficult to breed whether for selective breeding or the basic act of propagating the species.
They won’t change sex if there is an imbalance (functional hermaphroditism occurs in more than 450 fish species), need precise temperature and water conditions, or even need a full moon serenade to get in them in the mood.
Under ideal conditions, female Swordtail Fish mate freely and can give birth to as many as 80 babies every 28 days. Since this is precisely a lunar cycle perhaps that moonlight serenade wasn’t so far off the mark after all.
They breed without intervention as long as they are in a healthy habitat. Lush vegetation, good nutrition, and a healthy home are about all they need to spawn.
A few days after mating the female belly will start to swell noticeably as the babies begin to gestate through to live birth. Here is an excellent video that demonstrates swordtail pregnancy.
During this time it is important to prepare the nursery; you can either use a separate tank or a tank divider to keep the juveniles.
Just make sure you are ready to reconfigure your tank or have the spare bedroom ready in time for the deliveries. If not they are liable to be eaten only moments after their birth.
You also need to stock up on food for your growing family. At each stage of their development, they will be able to eat larger and more complex items. Larvae, fry, and fingerlings (each of the main early life-cycle stages of fish) can’t eat the standard large-sized pellets and flakes.
In the wild, they would simply be eating smaller versions of normal natural food sources. In captivity, we just need to provide them with similar alternatives. Most people use powdered fish food, or newly hatched brine shrimp to feed their newborns.
Once they have evolved into fingerlings they will be big enough to start introducing regular adult foods, much like a human adult’s do with infant children.
It is at this point they can be re-integrated with their parents, just be wary of any possible skew to the new male to female ratio with your new additions.
Final Thoughts
If you create a space similar to their own biome your Swordtail Fish community will flourish.
These easy to keep fish are visually beautiful, naturally disease resistant, and reproduce both easily and prolifically.
Just know that with their adept color vision (including infrared) they may be watching you just as intently as you do them from across the room that you share together.
