Calico Swordtail

The calico swordtail is a selectively bred form created by crossing the green swordtail and platy. The fish has an elongated body 14–16 cm long, with the characteristic extended lower ray of the tail fin in males, called the sword. The coloration combines three colours—white, red or orange, and black—forming a mottled pattern reminiscent of the Japanese Koi carp of the Showa variety. Sexual dimorphism is pronounced: males are slimmer and possess a gonopodium, while females are larger and bulkier.

In nature, Xiphophorus hellerii inhabits waters in Central America, including rivers and streams in Honduras and Guatemala. The calico variety is entirely artificially bred and does not occur in the wild. In the aquarium, the fish adapt to a wide range of parameters: a temperature of 16–28 °C, water pH of 7.0–8.0, and water dH of 10–30.

This is an active and peaceful fish suitable for keeping in community aquariums with similarly-sized species. Males can display intraspecific aggression, so it is recommended to keep them in a ratio of at least 2–3 females to one male to reduce competition. The species inhabits primarily the middle water level. It is compatible with most calm fish, but avoid tank mates that are slow-moving species with long fins.

The calico swordtail, like other livebearing fish, is generally regarded as an undemanding aquarium inhabitant. This fish adapts readily to a wide range of temperatures and water chemistry parameters and has no special requirements for tank setup. It can even be kept in slightly brackish water. Care is often straightforward. For example, in a dedicated swordtail tank, a heater is sometimes unnecessary, and if the tank volume is large and the number of fish is low (1–2 individuals per 100 litres), a simple air-lift filter is sufficient. Regular maintenance includes a 15–20% water change weekly and removal of accumulated organic matter such as uneaten food and waste. Regarding feeding, the calico swordtail readily accepts a variety of suitably-sized foods. A varied diet that includes dry, frozen, and live foods is optimal. However, daily feeding can be based entirely on standard flakes or pellets. These fish coexist peacefully with their own kind and other non-aggressive freshwater species. Avoid aggressive or territorial neighbours. Swordtails can hybridize with related species such as platies and mollies, producing hybrid offspring, which may raise questions about keeping them together.

Swordtails are omnivorous fish. The diet should include quality dry foods such as flakes or pellets, as well as plant-based supplements like spirulina or blanched vegetables. Foods containing carotenoids help maintain colour brightness. Feed once or twice daily in small portions that the fish consume within several minutes.

These fish are livebearers, which makes reproduction relatively simple. Fertilization is internal, by means of the gonopodium. Pregnancy lasts about 4–6 weeks, after which the female gives birth to fully-formed fry. These fish lack parental instinct, so for fry survival, dense plant growth or a separate rearing tank is necessary. Fry can immediately consume small specialized foods.

With proper keeping conditions and regular water changes, the fish remain healthy. Common problems include infections caused by protozoa or bacteria, often arising from poor water quality or overstocking. Prevention through quarantine of new fish and substrate maintenance is important. They are sensitive to sudden changes in water chemistry.

When purchasing, choose active fish with clean fins and no visible spots or film on the body. Ensure the belly does not appear sunken and behaviour is not sluggish. Avoid individuals that remain at the surface or constantly hide. Buy from reputable sources where tank density and hygiene standards are observed.