Black Swordtail

Looks how to spot one

scales

The Black Swordtail has a sleek, elongated body typical of swordtails, covered in small scales. Its most striking feature is the solid black colouration across the whole body, with bright fins that contrast beautifully. Males develop the characteristic 'sword', a long, pointed extension from the lower part of the tail fin.42

Personality what they are like

Black Swordtails are generally peaceful and social fish that do well in community tanks. Males can be a bit pushy with each other, so it is best to keep several females for every male to spread their attention and reduce squabbling.43

Daily activity how busy a day looks

They are active swimmers that enjoy exploring all parts of the aquarium. A tank of at least 100 cm (about 40 inches) in length is recommended to give them enough space to swim freely.4

Grooming and care the hands-on bits

Very low maintenance. Regular partial water changes and a good filter are enough. They are hardy and suitable for beginners. A tight-fitting lid is essential because swordtails are known to jump.45

Home where they are happiest

They prefer a well-planted aquarium with plenty of hiding spots (caves, dense plants) and open swimming areas. Water should be hard (GH 10-30, KH 5-20), pH 7.0-8.5, temperature 22-28 °C. A minimum tank size of 20-30 gallons (about 75-115 litres) is recommended for a small group.45

Food basics what goes in the bowl

Omnivorous. They eat high-quality flake or pellet foods with vegetable content, plus live or frozen foods such as brine shrimp, bloodworms, daphnia and mosquito larvae. Blanched vegetables like zucchini or cucumber are also appreciated.43

Company who they like around

They are shoaling fish and should be kept in groups of at least 10 individuals. A mix of different colour varieties works well. Provide plenty of hiding places for females to escape male attention. They are peaceful and can live with other community fish of similar size and temperament.43

The story where it all began

The Black Swordtail is a selectively bred colour variety of the wild Green Swordtail (Xiphophorus hellerii), which naturally lives in fast-flowing rivers and streams of Central America. Through many generations of careful breeding in captivity, aquarists developed this striking all-black form. It differs from the wild type mainly in colour: the wild fish is olive green with a red or brown stripe, while the Black Swordtail has a solid black body with bright fins. In all other respects, size, shape, behaviour and care needs, it remains the same as the wild species.245