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Black Swordtail
Xiphophorus hellerii
Animalia›Chordata›Actinopterygii
Variety of Swordtail · black
📍 Central America
A selectively bred swordtail variety featuring solid black or deep charcoal coloration while retaining the characteristic elongated lower tail extension of males. Hardy and active, it does well in community tanks of 20+ gallons with hard, alkaline water and tankmates that won't nip fins.
Care Guide
Diet
Black Swordtails are omnivorous and should be fed high-quality flake food or pellets as a staple, supplemented 2-3 times weekly with frozen foods like brine shrimp, bloodworms, or daphnia. Include vegetable matter such as blanched spinach or algae wafers weekly to support digestive health. Feed small amounts once daily, only what they can consume in 2-3 minutes.
Behavior
Active and peaceful mid-water swimmers that spend most of their time exploring the tank and grazing on algae. Males display characteristic sword-like tail extensions and may exhibit mild territorial behavior toward other males, though they rarely cause serious harm in adequately sized tanks. They are social fish that thrive in groups and appreciate plants for cover and security.
Breeding
Breeding in captivity is relatively easy as Black Swordtails are livebearers that reproduce readily in established tanks without special conditioning. Females produce 20-100 fry every 4-6 weeks; provide dense vegetation or a breeding box to protect fry from predation by adults. Separate fry into a nursery tank and feed infusoria or finely crushed flakes until large enough to join the main tank.
Tank Mates
Similar size, peaceful temperament, and identical water parameter requirements make them ideal companions
Fellow livebearers with matching water needs and peaceful behavior; compatible in community settings
Peaceful schooling fish that thrives in slightly alkaline water; minimal competition for resources
Algae grazer that occupies different ecological niche; prefers hard water like swordtails
Nocturnal algae eater that helps maintain tank cleanliness without competing for food or space
Common Diseases
Fin Rot
Frayed, discolored, or deteriorating fin edges; lethargy and loss of appetite
Perform 25% water changes every 2-3 days, maintain pristine water quality, and treat with aquarium salt (1 teaspoon per 5 gallons) or antibacterial medication if severe
Ich (Ichthyophthirius multifiliis)
White spots covering body and fins, excessive scratching against objects, rapid breathing
Raise water temperature to 28-29°C, perform daily 25% water changes, and treat with ich medication or salt therapy over 7-10 days
Velvet Disease
Fine golden or rust-colored dust on body, clamped fins, lethargy, difficulty breathing
Dim lighting to reduce stress, raise temperature to 28°C, and treat with copper-based medication or salt; isolate affected fish if possible
Dropsy
Swollen abdomen, protruding scales, lethargy, loss of appetite, pale coloration
Isolate affected fish immediately, perform frequent water changes, feed high-quality foods, and treat with antibiotics; prognosis is often poor
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Varieties
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Water it likes
- ph
- 7.0–8.3
- ammonia
- 0 ppm
- nitrate
- <20 ppm
- temperature
- 64–79°F (18–26°C)