Not many people in the fish hobby hear of sleeping sickness anymore. Sleeping sickness is now considered one of the most rare behavioral abnormalities exhibited by koi. However, because of the seasonal changes, I thought it best to bring this "sickness" back into the light, especially for new koi owners.
Sleeping sickness is not really a disease or sickness. As mentioned above, it is a behavioral abnormality that only koi display. Not only that, but sleeping sickness has even more "requirements". No koi older then two years old will experience sleeping sickness. Also, for sleeping sickness to occur, water temperatures need to be only a few degrees above freezing consistently for at least a week.
The symptoms of sleeping sickness can be frightening to any new koi owner. A young koi will float to surface of the pond, or underneath the ice of a frozen pond, and appear dead. This occurs because the young koi's metabolism has dropped so low that the body simply goes into shock. Some could compare this state to that of a temporary coma. The body has no responses while kept in water below 50 degrees.
How is one to be sure that their young koi really is alive then? First, lightly salt your water with aquarium salt. Then every day raise your temperature three or four degrees. If you are not able to raise your temperature in a pond setting, then bring the koi inside. Raise the temperature up to 70 degrees fahrenheit, and stop there. Also bring the salt level up to .3 . Needless to say, you will need to bring this level back down with future water changes.
If gill movement occurs, no matter how slight, there is a guarantee that your koi is suffering from sleeping sickness. However, only if the fish becomes responsive, the sleeping sickness will not take the koi's life. If the young koi has gill movement, but does not cease "floating" and return to normal movement or activity, it is best to consider putting the koi to sleep before its body shuts down from starvation.
The best hope for preventing sleeping sickness is keeping your outside koi pond at a constant temperature. If this cannot be done, please consider bringing your young koi (any koi under two years of age) inside for the winter.
Because of pond heaters and new covering techniques, the majority of experienced pond hobbyists and koi keepers probably have never experienced sleeping sickness. This is not true though for the large amount of people who buy young koi as beginning hobbyists, and when winter comes have no idea what has happened to their young koi. Sleeping sickness can feel like a beginning koi keeper's worst nightmare, but with a little knowledge the experience can be a great opportunity to further your knowledge of koi care during the winter season.
Melodium