The ulcers on the koi cannot heal on their own. If not treated in time, they will become more serious and even lead to death. When ulcers are found on the koi, you must first check whether the ulcers on the koi are caused by trauma. If not, it is likely to be saprolegnia, which is a fungal infection on the body surface. In this case, timely treatment is required.

Treatment methods for koi saprolegnia:

1. The sick koi must be isolated from other koi and raised alone. For fish, the fish tank needs to be thoroughly cleaned and soaked in a mixture of 0.04% table salt and 0.04% baking soda. After soaking, replace the water and raise the water temperature of the fish tank to 30 degrees, and then disinfect and clean it once a week.

2. Clean the wound of the sick koi with 4% iodophor. After cleaning, use formalin 100 to 250ppm and flow bath for one hour.

3. Apply nitrofurazone to the wound and change the water every day. If possible, adjust the water temperature to about 30 degrees, which is beneficial to the recovery of the wound.

4. You can also soak the wound with 3% salt solution for 5 minutes every day, and apply nitrofuracil ointment to the wound for several days until the condition improves.