Buy pond heaters online http://www.heatingyourpond.com/Pond-Heaters.htm... Bacteria and parasites can grow more quickly in warm water. The koi fishes system takes time to adjust but the disease organisms do not. Raise the temperature from ambient at 3 - 5 degree intervals every 24 hours to 80 - 84 degrees Fahrenheit. Maintain a stable temperature with less than 2 degrees variable per day Treat with 0.3% salt and parasiticides or antibiotics during the adjustment period, and continue with medication if necessary until cure is affected. Maintain temp. for 4 - 6 weeks after cure, then slowly drop the temperature to match that of the pond water. This will ensure a stronger Koi and ease the fishes transition back to the pond.
