The ideal water temperature for koi ranges between 65 and 75 degrees Fahrenheit. Koi are hardy fish that can tolerate a range of conditions, but they thrive best within this temperature window. At these levels, their metabolism functions efficiently, their immune systems remain strong, and they are most active and responsive.
When the temperature drops below 50 degrees, their metabolism slows down significantly, and they should not be fed, as their digestive systems cannot process food properly. In the summer, if water temperatures rise above 80 degrees, oxygen levels can drop and stress the fish, so shade or aeration may be needed. Keeping the temperature stable and within the preferred range supports koi health and reduces the risk of disease.
