Description
Temperature
Koi are pretty temperature-resistant— they can even hibernate under ice in winter. Just be sure your pond is at least three feet deep— otherwise, it could freeze solid, and koi aren't that tough. When they live indoors, koi prefer cool water between 65 and 75 degrees F (18 to 24 C).
Water Conditions
Most tap water is around 7.4 to 7.6, which is perfect for Koi, as they do best in water at 7.2 - 8.0. Koi can actually tolerate a wide range of PH, from 6.5 all the way up to 9.0, but they cannot tolerate a rapid change, no more than 0.2 per hour. Acceptable rang for happy Koi is 7.4 - 8.4.
