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Adult size + growth rate
How big does a Koi get?
TL;DR Koi grow 24-36 inches in proper ponds. Show-grade koi reach 28-30 inches. Largest documented koi exceed 4 feet.
Growth timeline Stage Size Juvenile 4-6 inches (purchase) Six Months 8-10 inches One Year 12-14 inches Three Years 20-24 inches Adult 24-36+ inches
Factors that affect maximum size Pond size: minimum 1,500g for proper growth Diet: Saki-Hikari Multi-Season for show-grade Genetics: Japanese-bred koi reach largest sizes Water quality + temperature Tank size requirement 1,500+ gallon outdoor pond minimum
Full Koi care guide Browse the full Koi care guide for water parameters, diet, tankmates, and breeding details. Use the stocking calculator to plan around adult size, not juvenile size.