Could I keep cardinal tetras with goldfish by running the tank at 72F?

72F is at the very top of the goldfish range and the bottom of the cardinal range. Goldfish will be overheated and stressed. Cardinals will barely tolerate it but will not display their best coloration or schooling behavior.

What tropical fish can live with goldfish in a coldwater tank?

None. Goldfish need coldwater conditions below 72F. No tropical fish thrives at goldfish temperatures. Keep goldfish with other coldwater species or move the goldfish to a heated tropical tank with appropriate tankmates.

Can I put cardinal tetras in an outdoor pond with goldfish in summer?

This only works in temperate climates where pond temperatures stay between 73-81F during the warm months. Most summer ponds get hotter than 81F, which kills cardinals. Winter temperatures below 73F also kill them. This is not a practical combo.

Can Cardinal Tetra Live With Goldfish?

By Alex WalshLast reviewed Apr 18, 2026

No, cardinal tetras and goldfish share no temperature overlap, with cardinals needing tropical warmth (73-81F) and goldfish requiring cool water (60-72F).

Why

Cardinal tetras are tropical fish needing 73-81F, with 78F being ideal.
Goldfish are coldwater fish thriving at 60-72F, with 65F being ideal.
The temperature overlap between these ranges is zero. There is no shared temperature that works for both.
Goldfish in tropical water above 75F develop heat stress, accelerated aging, and shortened lifespans.
Cardinal tetras in coldwater below 73F become sluggish, stop schooling tightly, and die from temperature shock.

Minimum shared tank

30 gallons

What could go wrong

Either the cardinals freeze or the goldfish overheat, depending on which temperature you choose, and neither species can survive the opposite extreme.

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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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 dojo loaches, weather loaches, or other coldwater species in ponds or unheated tanks. Cardinal tetras thrive in tropical soft-water communities with neon tetras, rummy nose tetras, or harlequin rasboras at 78F.