SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/fish-goldfish-room-temp

Does a goldfish tank usually need a heater?

No, goldfish do fine at room temperature.

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  1. No, room temperature is fine ✔
  2. Yes, always set to 85°F
  3. Only if the fish is old

Why: Goldfish and other temperate or coldwater fish do fine in room-temperature water. Tropical fish are different: they need a heater. Know which kind you are buying before you buy equipment.

Huh, didn't know that: Goldfish eat less in cool water and more when it is warmer (but not hot).

The dad joke
What do you call a fish with two knees? A two-knee fish.
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References

Answer: No, room temperature is fine. Goldfish and other temperate or coldwater fish do fine in room-temperature water. Tropical fish are different: they need a heater. Know which kind you are buying before you buy equipment.

  1. Merck Veterinary Manual (pet owners): Providing a Home for Fish www.merckvetmanual.com/all-other-pets/fish/providing-a-home-for-fish
    Goldfish and certain other temperate-water or cold-water fish do fine in water that is room temperature.
    Checked 2026-10-11.

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Fish & AquariumsWhy can goldfish be a poor match for many tropical fish?Fish & AquariumsDoes a betta fish need a heater in most homes?Fish & AquariumsWhy does every heated aquarium need a thermometer?

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