Montezuma Swordtail

Adult males can reach 4–5 cm in length, and it's worth noting that this size does not include the tail. The tail of males, thanks to elongated lower rays forming a characteristic "sword," can exceed the length of the fish's body by twofold. Their coloration is silvery, often with yellow or greenish iridescence. Several black speckles can be seen on the fish's body, most noticeable on the dorsal fin. Females are similar in size, but their coloration is less pronounced, predominantly gray. A distinct black stripe runs along the entire body of the females, extending from the head to the tail. It is important to note that female specimens do not possess such a prominent "sword."

The natural habitat of these fish covers the northeastern regions of modern Mexico. They prefer to live in numerous river systems that flow from the hilly terrain to the Gulf of Mexico. Montezuma Swordtails are often found near the shoreline, where they hide among dense thickets of aquatic vegetation.

Males of this species display a temperamental character, often competing with each other for territory and the attention of females. In a small aquarium, it is recommended to form a harem group, where one male is kept with several females. They are peaceful towards other fish species. Montezuma Swordtails are compatible with many freshwater species of similar size and temperament. However, cohabitation with fish that tend to nip or damage fins, such as some barb species, should be avoided.

For keeping 4–5 Montezuma Swordtails, a suitable aquarium volume starts from 100 liters. When setting up the tank, it is important to provide hiding places. These can be dense thickets of live plants, various branched snags, or artificial decorative elements. This swordtail species is considered undemanding to keep. Maintaining a slightly alkaline hydrochemical water composition with moderate to high hardness (dGH) is crucial. To keep organic pollution levels low, weekly partial water changes with fresh water and a reliable filtration system are necessary. It is also recommended to create a moderate internal current, effectively mimicking the natural water flow in a river, which is easily achieved with a powerful internal filter.

The fish readily accept all types of food intended for aquarium inhabitants. The recommended daily diet can include dry flakes or granules, which can be supplemented with live or frozen brine shrimp, bloodworms, daphnia, and other invertebrates.

Under favorable conditions and with a balanced diet, spawning can occur every 4–6 weeks. This is the incubation period. A distinctive feature of swordtails is livebearing — females give birth to fully formed fry. On average, a single female's brood numbers from 10 to 30 individuals. Within an hour of birth, the fry are ready to eat. Since parental instincts are not developed in these fish, there is a risk of predation by adult specimens on their own young.

The likelihood of diseases increases if the fish are kept in unsuitable conditions, receive poor-quality food, or are injured. In conditions close to natural, cases of disease are extremely rare.

When choosing Montezuma Swordtails, pay attention to the fish's activity and the cleanliness of their skin. Healthy individuals should show curiosity, swim actively, and have no visible damage, ulcers, or white film on their scales. Avoid purchasing fish that stay at the surface, breathe heavily, or have clamped fins, as this may indicate problems with water quality in the aquarium or the presence of infections. — Inspect the fins: they should be intact, without signs of splitting or erosion. — Check behavior: males in the store often display territorial skirmishes, which is a sign of their normal vital activity. — Ensure there is no emaciation: the fish's belly should not be sunken, and the body shape should conform to species standards without spinal deformities.