I keep only female guppies and female swordtails. Is that combination safe?

Female-only tanks eliminate the fin-nipping aggression from male swordtails. Females of both species are peaceful and can coexist in a planted 30-gallon tank with plenty of cover.

My male swordtail is chasing my guppies. Can I add more males to spread out the aggression?

Adding more males makes it worse. Male swordtails compete with each other as well, creating a tank with constant chasing and no peaceful periods. Separate the species or keep a single male with multiple females.

Would a heavily planted tank reduce the aggression?

Dense planting helps guppies find refuge but does not eliminate the stress of constant pursuit. The guppies will survive but not thrive. A species-appropriate tank is a better long-term solution.

Can Guppy Live With Swordtail?

By Alex WalshLast reviewed Apr 18, 2026

No, guppies and swordtails are a poor match because male swordtails are semi-aggressive toward small, colorful livebearers and will harass guppies relentlessly.

Why

Male swordtails grow to 5-6 inches and are semi-aggressive toward smaller fish, especially colorful species with flowing tails.
Guppies reach only 1-2.5 inches and have long, flowing fins that trigger chasing behavior in active male swordtails.
Male swordtails will chase guppy males and females continuously, stressing the guppies and preventing normal feeding.
Swordtails are top-level swimmers and outcompete guppies for food at the surface, where guppies prefer to feed.
Even though both species prefer similar temperatures (72-82°F) and alkaline pH (7.0-7.8), temperament incompatibility makes cohabitation impractical.

Minimum shared tank

20 gallons

Shared temperature range

72-82°F

What could go wrong

Guppies will hide constantly and lose body condition from stress. Fin nipping from persistent swordtail chasing is common, and secondary infections from damaged fins follow. Guppy populations may also crash if females cannot access food away from aggressive swordtail males.

If you keep them in separate tanks

Sized for the 20 gallon minimum this pairing needs. Affiliate links — we earn a small commission if you buy through them.

AquaClear 30 Power Filter

Oversized filtration is what lets you stock two species together without water quality crashing. Rated for a tank slightly larger than the 20 gallon minimum.

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Eheim Jager 150W Thermostat Heater

Holds a steady temperature inside the 72-82°F window both species need.

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API Freshwater Master Test Kit

Keep ammonia, nitrite, and nitrate in check. Two-species tanks have more bioload and less margin for error than single-species setups.

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Better pairings to consider

Platies share swordtail water preferences and calm temperament, making them ideal tankmates. Molly and platy species are also compatible with swordtails and do not trigger the same chasing behavior. Guppies do well with corydoras, ember tetras, and small rasboras.