Koi grow quickly and get very large. Keep mature koi in an outdoor pond of at least 3 feet deep, with at least 50 gallons of water per fish. Young koi can be kept indoors in an aquarium of at least 29 gallons. Put the aquarium in a quiet area out of direct sunlight and drafts.

How much does it cost to own a koi fish?

One koi fish typically costs between $10 and $380. Lower costs usually are for koi from a pet store whereas higher costs come from a breeder. Some koi can cost $10,000 or more.

Are koi fish expensive to maintain?

The average yearly koi pond maintenance cost is around $3,150, with basic ponds starting around $2,940. How this breaks down: The average cost for spring maintenance is $1,200 ($990 for basic ponds) Summer filter and fall filter cleaning are $500 each plus $400 for fall netting.