
Common disease signs are ulcers, red sores, red mouth, or (in more advanced cases) the fish can swell up internally, giving the appearance of a pine-cone, with its scales and/or eyes popping out. Generally, an infection is triggered by injury or environmental stressors. This condition is usually caused by Aeromonas hydrophilla, but other species of Aeromonas as well as Pseudomonas and a few less common bacterial genera can cause the disease. Ulcer Disease (synonyms: Red Sore, Red Mouth, Hole-In-Body Disease, Dropsy, Pine-Cone Disease, Pop Eye) Therefore, we have put together a page covering each of these issues. Koi & Goldfish health is also highly dependent on good nutrition, water quality and environmental conditions. Therefore, when a disease episode is triggered, it is absolutely critical to determine the cause, and fix it so that after you treat the disease it does not have the opportunity to reoccur. The most important concept to understand with fish health is that many parasites and diseases are present in every Koi pond, but they only trigger a disease episode when the fish are under some sort of stress, resulting from poor water conditions, rough handling, bad nutrition or harassment by a predator. As an example, while you will not find microscopic photos of Koi Parasites with detailed explanations of their life cycles here, you will find descriptions of how infected Koi will behave and recommendations on what you should do to treat them and/or what you can do to avoid the problem in the future. Instead of handling it comprehensively, we will hit on the topics that are important to the average Koi owner.


Koi and goldfish disease is a broad topic that is the basis of many books.
