Koi vs Goldfish
Pond royalty or tank classic? Side-by-side.
Our verdict
It comes down to space. Indoors with an aquarium? Goldfish, no contest — koi outgrow every tank. Have a garden pond of 1,000 gallons or more? Koi are generational pets that can outlive their keepers’ dogs, cats and sometimes their mortgages.
Common questions
Can koi live in a fish tank?
Only as juveniles. Koi reach around 24 inches and need pond volumes — roughly 1,000 gallons and up — to stay healthy. If you’re shopping for an indoor aquarium, choose fancy goldfish instead.
Can koi and goldfish live together?
Yes — in a pond. Both are peaceful cold-water cyprinids with similar needs. Just make sure small goldfish aren’t competing with much larger koi at feeding time, and skip delicate long-finned varieties.
Which costs more, koi or goldfish?
Koi. Quality pond koi start around $250 and show-grade fish climb quickly from there, while beautiful fancy goldfish start around $60. Factor in the pond itself — that’s the real koi investment.