Can Molly Live With Swordtail?
Yes, mollies and swordtails share a 20-gallon tank well, both preferring hard alkaline water and active upper-level swimming.
Why
- Both species are livebearers with near-identical water preferences: 72-82°F and pH 7.0-8.3, one of the widest overlaps in this batch.
- Mollies reach 4-5 inches and swordtails reach 5-6 inches, close enough that neither can predate on the other.
- Swordtail data lists mollies as compatible and molly data lists swordtails as compatible, a strong mutual endorsement.
- Both species thrive in hard, alkaline water and do not require soft or acidic conditions that would stress either fish.
- Both are active top-level swimmers, which means they share space without competing with bottom dwellers.
What could go wrong
Both species breed readily, and a mixed male-female tank will produce large numbers of fry that outgrow the tank quickly.
Gear for a shared tank
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.
Eheim Jager 150W Thermostat Heater
Holds a steady temperature inside the 72-82°F window both species need.
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.
Related compatibility questions
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