If koi catch a cold, stop feeding it first. Sick fish will lose their appetite and even don't eat, so feeding is meaningless, and food will become residual bait when it enters the water, which will also pollute the water quality to some extent, so it is necessary to stop feeding and wait until they recover before continuing feeding.

The main reason for catching a cold is that the temperature has changed too much. In order to prevent the disease from getting worse and recover as soon as possible, it is necessary to pay attention to controlling the water temperature. Although koi fish is a wide-temperature fish and can endure low temperature, it is best to control it above 20 ℃. If it is necessary to heat up, the daily increase should not be too large, and the maximum increase should be 2 ℃ a day.

If the cold is serious, it needs to be treated with drugs. Prepare a separate fish tank, pour the original tank water into it, add a little baking soda, and soak the fish in it, which can promote metabolism and enhance its vitality. It can also add a certain amount of sea salt, which can also play a role in sterilization.

Prevention of colds is mainly to control the temperature to avoid rapid temperature drop. If koi is cultivated outdoors, the fish pond should also do a good job of wind protection. If the temperature is too low in winter, it may freeze, so it is best to deepen the water level, so that the fish can move below without being frozen. In addition, drill a hole in the ice to prevent lack of oxygen.