How big do koi grow in a 1500 gallon pond?

In a 1500-gallon pond, koi can typically grow to be between 18 to 24 inches long, depending on factors such as the pond's environment, water quality, and the number of koi present. With optimal conditions and proper care, some koi may even reach sizes of up to 36 inches. It's essential to manage stocking levels and provide adequate filtration and aeration to support their growth.