Head to head
Swordtail vs Platy
The swordtail and the platy are near the top of the list of easiest, most popular aquarium fish, and it shows, since the two are so closely related that a huge share of the colour forms sold today are hybrids of both.
| Swordtail | Platy | |
|---|---|---|
| Genus | Xiphophorus hellerii | Xiphophorus maculatus |
| Body shape | Long, slender, torpedo-like | Short and deep-bodied |
| Adult size | To ~14 cm with the sword | To ~6 cm |
| The sword | Present in mature males | Absent in both sexes |
| Activity | More active, prone to jumping | Calmer, less jump-prone |
| Interbreeding | Crosses freely with the platy | Crosses freely with the swordtail |
| Water needs | Hard, neutral to alkaline | Hard, neutral to alkaline |
| Best for | A slightly larger, taller tank | A modest first aquarium |
Swordtail vs Platy: common questions
Can swordtails and platies be kept together?
Yes, and they are often kept in the same tank without any problem, since both want the same hard, stable water and similar food, and neither is aggressive toward the other under normal conditions. The one thing to know is that they can and will interbreed if both sexes of each are present, producing hybrid fry that show a mix of features, sometimes a smaller sword or an unusual colour pattern. This is harmless and common in mixed livebearer tanks, and many of the fancy strains sold in shops already carry genes from both species, so a certain amount of blending has already happened well before the fish reaches a home aquarium.
Which is easier to keep, a swordtail or a platy?
The platy is usually considered marginally easier, mainly because of its smaller size and slightly calmer temperament, which suits a modest first tank well. The swordtail is not much harder, but it grows larger, is a stronger swimmer, and is more prone to jumping, so it needs a bit more swimming room and a secure lid. Both are extremely forgiving of ordinary tap water and beginner mistakes compared with softer-water fish like tetras, and both breed readily, so either is a sound choice, with the platy having a slight edge for the smallest tanks.
Why do some swordtails not have a sword?
A sword only develops on mature males, so juveniles of both sexes and all adult females are naturally swordless, and a young male has not yet grown his. In addition, some captive strains have been bred specifically without the extended sword ray, or with it much reduced, for keepers who prefer a more platy-like body shape, and heavy crossbreeding with platies over generations can also produce swordtail-type fish with a short or absent sword. So a swordless fish sold as a swordtail is not necessarily wrong, since it may simply be young, female, or a bred or hybrid form.