Green Swordtail

The main distinguishing feature of the species is the elongated lower rays of the caudal fin with a black outline, which remotely resemble a sword. Adult specimens reach a length of 14–16 cm, including the "sword." The fish's coloration is silvery with noticeable green-turquoise hues. A purple stripe runs along the body, and the dorsal fin and tail are yellow. Males are smaller but their coloration is brighter, and they possess a characteristically modified anal fin — the gonopodium, which is tube-shaped and used for fertilization. Females, in turn, are larger and lack the "sword" on their caudal fin. It is important to note that there are many artificially bred varieties, including hybrids with Platies, which differ in a variety of colors, body patterns, and fin shapes. Detailed information on the characteristics of each variety is presented in separate materials.

The homeland of this fish species is Central America; originally, the natural distribution of swordtails covered territories from Mexico to Honduras. They inhabited numerous river systems flowing into the Atlantic Ocean. Nowadays, thanks to the activities of aquarists, their habitat has significantly expanded. Green Swordtails can now be found on almost all continents, with the exception of Antarctica, where the climate does not allow them to survive, being located in tropical and equatorial climate zones.

Male swordtails often compete with each other, striving to achieve a higher position in the hierarchy and attract females. This rivalry is usually demonstrative, without actual skirmishes or injuries, which allows them to be classified as peaceful species. They get along well with many other calm, non-aggressive fish of comparable size. However, it should be remembered that some fish species, such as barbs, tend to damage or nip the long fins of their tank mates. Given the unique structure of the Green Swordtail's caudal fin, they could potentially suffer from such behavior by barbs.

For the comfortable keeping of 3–4 fish, the optimal aquarium volume starts from 100 L. The choice of decorations does not play a decisive role, but observations show that fish feel better in conditions mimicking a riverbed: with moderate current, rocky substrates, and driftwood. Lighting should not be excessively intense; shading can be provided by tall plants that reach and spread across the water surface. A key condition for successful keeping is maintaining high water quality within acceptable temperature values and hydrochemical parameters. For this, the aquarium is equipped with everything necessary, primarily a filtration system, and a number of mandatory procedures are regularly carried out. These include weekly partial water changes, removal of organic residues (uneaten food, excrement), and cleaning of decorative elements and tank walls. Swordtails can tolerate slight salinity — roughly up to 2–3 grams of salt per litre — but they do not need it.

In natural conditions, the diet of swordtails consists of small invertebrates, such as aquatic insects and their larvae, as well as crustaceans, supplemented by algae and plant fragments. This omnivorous diet allows for successful feeding with most available dry, frozen, and live foods. Many manufacturers offer specialized foods for Swordtails, which can serve as the main part of their daily diet.

Under favorable conditions, spawning occurs regularly, without pronounced seasonality in an artificial environment. During reproduction, the alpha male actively circles the female, demonstrating his readiness to mate. When the female is ready, she accepts the courtship. Fertilization occurs inside the female's body. Fry appear fully formed, bypassing the egg stage. The incubation period lasts about a month. The female has the unique ability to control the fertilization process, retaining the male's sperm inside her for several months. For example, if the water temperature drops or nutrition is insufficient (if the owners are on vacation), the fertilization process can be delayed. Adult fish do not show parental care and may eat their offspring. To preserve the brood, it is recommended to transfer the fry to a separate tank.

This species is considered hardy and quite undemanding. Nevertheless, selective varieties may be more sensitive to keeping conditions and more susceptible to diseases. At the first signs of illness, such as lethargy, refusal to eat, or changes in fin and body shape, it is necessary first to check the water parameters: the presence of dangerous concentrations of nitrogen cycle products, as well as pH and GH values. Often, the cause of diseases is unsuitable keeping conditions. If all parameters are brought back to normal, the fish's immune system may cope with the ailment on its own. Otherwise, medication will be required.

When choosing swordtails, pay attention to the overall activity of the fish: healthy individuals should be active, show curiosity, and not hide in the corners of the aquarium. Examine the scales and fins for damage, white film, or suspicious spots that may indicate infections. Avoid fish with clamped fins, unnaturally bloated or, conversely, severely sunken bellies. It is advisable to purchase individuals raised locally, as they are better adapted to tap water than imported specimens. Before purchasing, make sure there are no dead individuals in the fish tank, as this indicates poor keeping quality in the store.