Goldfish Tanks: Why the Bowl Has to Go
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Goldfish are often sold as starter pets, but their needs surprise people. Here's what Aqueon's care guide and federal and state agencies say. Product details are from the listings; we haven't tested them.
Space
Aqueon: goldfish "should never be kept in bowls, small aquariums or any unfiltered container! In addition to having relatively high oxygen demands, they grow to be quite large and generate a significant amount of waste." Its recommendation: at least 20 gallons per adult common, comet or shubunkin, and at least 10 gallons per adult fancy goldfish.
How large? Minnesota DNR says goldfish are typically 5 to 8 inches but "can reach close to 2 feet long," and USGS lists lifespans usually of 6 to 7 years with a recorded maximum of 30. Aqueon says properly cared-for goldfish "can live over 20 years."
Temperature
Aqueon says fancy goldfish do best at 68 to 74°F, and comets and shubunkins at 60 to 70°F. UF notes high temperatures can stress coolwater fish like goldfish. Purdue's 4-H manual says goldfish "should not be placed with tropical fish."
Filtration and water changes
Aqueon: "The filter should be slightly over-sized to accommodate high waste production." It suggests changing 10% of the water weekly or 25% every two weeks, and feeding only what they eat in 2 to 3 minutes, once or twice a day.
Fluval 207 Canister Filter
- For aquariums up to 45 gallons (title)
- Listed as up to 25% quieter than before
- EZ-Lift media baskets
Fluval AC70 Power Filter
- Hang-on-back filter for 40-70 US gallons (title)
- Media included (listing)
A tank to start with
By Aqueon's numbers, a 29 gallon tank fits one common goldfish or a couple of fancies. Tetra's 29 gallon kit includes a Whisper PF 30 filter; its included heater may not be needed if your room stays within Aqueon's goldfish range. A bigger filter is a sensible upgrade given Aqueon's oversizing advice.
Tetra 29 Gallon Aquarium Kit
- 30 x 12 x 18 in. glass tank, LED hood, per the listing
- Whisper PF 30 filter
- 200W heater and thermometer included
Aqueon Siphon Gravel Cleaner, Medium 9 in.
- For aquariums 15 to 35 gallons, per the listing
- Self-priming: up-and-down motion starts flow
- 6 ft hose with bucket clip
Never release goldfish
The U.S. Fish and Wildlife Service says released goldfish "become an invasive species that can live for up to 25 years and do real harm to the water quality and wild fish communities." Minnesota DNR says goldfish "reproduce rapidly and can quickly number in the hundreds or thousands." Rehome them through a store, club or another hobbyist instead. See why you never release aquarium fish.
FAQ
Gallons per goldfish?
20 for commons and comets; 10 for fancies (Aqueon).
Bowls?
No, per Aqueon.
How big?
Typically 5-8 in., up to nearly 2 ft (MN DNR).