My room is at 72 degrees. Can I keep both species together without a heater or chiller?

72 degrees is too cold for guppies long-term. At that temperature, they become lethargic, prone to disease, and stop breeding. Their colors fade. Goldfish are fine at 72 degrees, but you cannot satisfy both species in one tank.

Will goldfish eat adult guppies or just fry?

Fancy goldfish are slow swimmers and may not catch adult guppies, but common goldfish are fast and will swallow guppies whole. Even fancy goldfish will attempt to eat guppies and may succeed with smaller individuals.

Can I keep a single small goldfish with guppies in a tropical tank?

No. Tropical temperatures (76-82 degrees) stress goldfish and shorten their lifespan significantly. Goldfish kept in warm water develop health problems and live far shorter lives than they should.

Would a divided tank work?

A divided tank keeps the two species separated physically, but water parameters still mix through the filter and divider gaps. You cannot maintain cold water on one side and warm water on the other through a standard filter. Separate tanks are the only reliable solution.

Can Goldfish Live With Guppy?

By Alex WalshLast reviewed Apr 18, 2026

No, goldfish need cold water that is too cool for tropical guppies, and goldfish will eat guppies given the opportunity.

Why

Goldfish thrive at 60-72 degrees Fahrenheit while guppies need 72-82 degrees. The overlap sits at exactly 72 degrees, which is the upper limit for goldfish comfort and the lower limit for guppies. Neither species thrives at this single shared degree.
Goldfish grow to 6-12 inches (common types) or 4-6 inches (fancy types). Guppies stay at 1-2.5 inches. Even small goldfish will attempt to eat guppies if they fit in the mouth, and they often do.
Goldfish are coldwater fish adapted to unheated tanks. Guppies are tropical and require a heater. You cannot maintain a temperature that works well for both species simultaneously.
Guppies reproduce rapidly and goldfish will eat any fry they encounter. A single female guppy can produce 20-50 fry every 30 days, and the goldfish will work through them efficiently.
Goldfish produce massive bioload (approximately 4 times standard fish load) and need strong filtration and frequent water changes. This maintenance level is incompatible with keeping a healthy guppy colony.

Minimum shared tank

30 gallons

Shared temperature range

72-72°F

What could go wrong

Goldfish will eat guppies outright, and the cold-water requirement for goldfish makes it impossible to keep tropical guppies healthy long-term in the same setup.

If you keep them in separate tanks

Sized for the 30 gallon minimum this pairing needs. Affiliate links — we earn a small commission if you buy through them.

AquaClear 70 Power Filter

Oversized filtration is what lets you stock two species together without water quality crashing. Rated for a tank slightly larger than the 30 gallon minimum.

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Eheim Jager 200W Thermostat Heater

Holds a steady temperature inside the 72-72°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

Goldfish do well with other goldfish, dojo loaches, or weather loaches. Guppies do well with neon tetras, bronze corydoras, or cherry shrimp in a heated tropical tank.