How big do Koi get?

Koi fish can grow very fast.  The average Koi can grow to 24 – 36 inches!  The size of the pond, the amount of aeration, and feeding methods will affect the growth of the fish.  It is not uncommon for a small Koi to grow 2 – 4 inches a year in a backyard pond.  Colorful Koi which have been selectively bred can get to lengths of 36″ to 40″ and weigh up to 50 pounds.  Koi can be kept indoors in aquariums also.  The koi will grow to comfortably accommodate their surroundings.