Goldfish care: why they need more room than you think

The short answer: goldfish are not bowl fish or throwaway starter fish. They are large, long-lived, heavy-waste coldwater fish that need far more space and filtration than most people expect. As a widely used guideline, plan on roughly 20 US gallons for a single fancy goldfish and about 10 more gallons for each additional one. Common and comet goldfish grow much bigger, over a foot long, and really belong in a pond or a very large tank, not a home aquarium. Give them the room and the filtration they need and they can live well over a decade.

Why the bowl is a myth

Goldfish stay small in a small container only because poor water quality and stunting hold them back, and a stunted goldfish is a sick, short-lived one. In proper conditions they grow large and live a long time. Buy a goldfish for the adult it becomes, not the tiny one in the bag.

Tank size, honestly

  • Fancy goldfish (fantail, oranda, ryukin and similar): around 20 gallons for the first fish, plus roughly 10 per extra fish. They are round-bodied and slower, so they suit an aquarium.
  • Common, comet and shubunkin goldfish: these grow very large and fast, and are best suited to a pond or a tank measured in the many tens of gallons.

See what we have in the goldfish collection, and ask us which type you are looking at before you commit to a tank size.

Filtration for a messy fish

Goldfish eat a lot and produce a lot of waste, so they need more filtration than a tropical tank of the same size. Oversize the filter: aim for strong turnover and plenty of biological media. Our filters and filter media collections have the capacity these fish demand. Regular water changes are not optional with goldfish; they are the main thing keeping the water safe.

Coldwater, not tropical

Goldfish are a coldwater species and do well at ordinary room temperature, so they usually do not need a heater, though they do appreciate stable temperatures rather than swings. Keep an eye on water quality with a test kit, and always treat tap water with a water conditioner before it goes in.

Never release a goldfish

Goldfish are invasive when released into local waters, where they can survive Alberta winters, breed and damage ecosystems. Never release a goldfish or dump tank water into a pond, storm drain or waterway. If you can no longer keep one, bring it to us or rehome it responsibly.

Related guides

Come and ask us

Fishkeeping goes better when a real person can look at your setup. Come into the store in Lethbridge, call us at 403-380-4506, or send us an email, and someone who keeps fish will help you get it right. Written by the team at Tropical Fish Imports.

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