Koi fish can grow. 1-year-old koi fish are 10-20 cm long, 2-year-old koi fish are 24-30 cm long, 3-year-old koi fish are 37-40 cm long, 5-year-old koi fish are 45-50 cm long, 10-year-old koi fish are 55-70 cm long, Koi fish over 10 years old can grow to 1-1.5 meters.

However, it should be noted that the size of the fish tank has a significant impact on the growth of koi fish. great relationship. In general, the koi fish in small fish tanks can only grow to two or three inches due to the restricted activity space.