Berlin Swordtail is a selectively bred color strain of the Green Swordtail, valued for its bold contrast and classic livebearer hardiness. It’s a long‑standing aquarium variety and remains popular in retail and hobbyist setups.
Overview
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Common Name: Berlin Swordtail
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Scientific Name: Xiphophorus helleri
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Type: Selectively bred color morph
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Origin: Captive-bred (derived from Central American wild stock)
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Adult Size:
- Males: 10–12 cm (4–5 in, including sword)
- Females: up to 14 cm (5.5 in)
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Lifespan: 3–5+ years
Color & Appearance
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Base Body: Bright red to deep crimson
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Posterior Half: Distinct solid black (often sharply divided at mid‑body)
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Sword (males):
- Elongated lower caudal ray
- Typically black or dark‑edged
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Females:
- Larger body
- Rounded caudal fin
- Red body with black rear, no sword
The high‑contrast red-and-black split is the defining feature of the Berlin strain.
Aquarium Care
Tank Size
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Minimum: 30 gallons
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Recommended: 40+ gallons (especially with multiple males)
Swordtails are very active swimmers and need horizontal space.
Water Parameters
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Temperature: 22–28 °C (72–82 °F)
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pH: 7.0–8.2
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Hardness: Moderate to hard (10–30 dGH)
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Flow: Moderate
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Filtration: Strong biological filtration preferred
Berlin Swordtails tolerate a range of conditions but show best color and health in stable, alkaline water.
Aquascape Recommendations
- Open swimming space
- Dense plants along the back and sides
- Hardy plants ideal:
- Vallisneria
- Java fern
- Anubias
- Echinodorus (Amazon swords)
- Floaters can help diffuse light and reduce stress
Diet
Omnivorous with important vegetable needs.
Staple Foods
- Quality flake or pellet with spirulina
- Vegetable-based formulations
Supplements
- Blanched zucchini, spinach, peas
- Live/frozen foods: brine shrimp, daphnia, bloodworms (treats)
A plant‑heavy diet helps prevent:
- Bloating
- Aggression
- Poor coloration
Temperament & Compatibility
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Temperament: Active, semi‑peaceful
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Behavior Notes:
- Males can be pushy with each other
- Occasional fin‑nipping in cramped tanks
Best Ratio
Compatible Tank Mates
- Platies
- Mollies
- Guppies
- Corydoras
- Bristlenose plecos
- Peaceful rainbowfish
Avoid
- Aggressive cichlids
- Known fin‑nippers
- Very slow or delicate species in small tanks
Breeding
Berlin Swordtails are livebearers and breed readily.
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Gestation: 24–35 days
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Fry per brood: 20–80+
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Breeding Difficulty: Easy
Breeding Notes
- Females can store sperm for multiple broods
- Color consistency may drift if crossed with other swordtail strains
- Dense plants or breeder boxes improve fry survival
To maintain true Berlin coloration, avoid cross‑breeding with red, pineapple, or wild-type swordtails.
