Treating Ulcers

How to treat an ulcer and dress the wound:

Treating an ulcer is not what koi keepers like to do. Doing it right the first time is important. The infection in the wound must be completely removed and disinfected.

Preferably the wound must be sealed. Lastly the bacterial load in the water must be reduced.

Always remove any rings and watches whenever Koi is handled. Get all equipment ready and within reach. It is a good idea to have a helper, especially the first time you do it. Anaesthetise the fish only if it is difficult to handle. (Fish of 25 to 55 cm typically fall in this category)
Quickly remove all necrotic (dead) tissue from the wound. Pull out scales that might hide infection. Using a scalpel or blade, scrape all signs of infection or redness around the periphery of the wound. The wound must be thoroughly cleaned. If this is done properly the first time, the procedure will not have to be repeated. If the infection is in bone or fin rays, cut or scrape it away clean. The tissue will re-grow. Disinfect the wound with an antiseptic (eg Savlon) and dab dry with paper towel. Apply a topical antiseptic such as Betadine or mercurochrome and again dab it dry. Seal the wound with a water resistant ointment such as Orobase or Wound Seal. (Wound Seal contains a powerful antibiotic and antiseptic and the previous step is therefor not required.) Blow it dry and place the fish in the recovery tub, keeping a close watch until it has recovered and can be moved back to the hospital tank. This procedure should take less than a minute.
Maintain a 0.3% salt concentration and the temperature at 20 – 24oC in the hospital tank to promote healing. Adding a mild antiseptic like StreriPond to the water can reduce reinfection.

Feeding an antibiotic food during this time will help the healing process towards a speedy recovery. However there are risks involved and proper consultation is needed with a professional. Inspect the wound every day. If the wound was cleaned properly, it will soon heal over without any further treatment. Any further signs of haemorrhaging in the area of the ulcer is an indication that cleaning was poorly done, or the infection has advanced too far and the fish is having trouble maintaining internal water balance. In such a case a professional should be called in to administer an antibiotic correctly and advise on further treatment.


Extracted and modified from Koi Handbook by Servaas de Kock & Ronnie Watt. (FireFly Books 2006) and expanded  Available on