Diving disease in koi is a condition characterized by "repeated diving and difficulty swimming." Its cause is currently unclear, and the cure rate is extremely low.
Main Symptoms
Affected fish typically display a cycle of "lying on the bottom for long periods → struggling to rise → taking a breath → sinking back to the bottom":
-
Bottom‑lying phase: Remains motionless at the bottom for several hours.
-
Ascent phase: Swims upward with noticeable body swaying and obvious effort, appearing to struggle.
-
Surface action: Takes a quick breath at the surface, then immediately sinks.
-
Repetition: The cycle may repeat dozens of times a day, with the fish gradually losing weight.
Two Main Theories About the Cause
Theory 1: Swim‑bladder inflammation (more widely accepted)
The swim bladder becomes inflamed due to bacterial infection or physical injury, losing its ability to regulate buoyancy. The fish can no longer control its ascent and descent normally and must "struggle‑swim" to breathe.
Theory 2: Water‑pressure theory (more controversial)
Suggests that in recirculating ponds deeper than 1.5 meters, significant pressure changes over time impair swim‑bladder function. However, this theory lacks scientific validation.
Current consensus: The exact cause remains unknown and may involve multiple factors, such as congenital swim‑bladder defects, chronic inflammation, or sudden changes in water quality.
Current Treatment Status and Prognosis
Key fact: There is no widely accepted effective treatment, and very few cases have been cured. Most affected fish eventually die from exhaustion or malnutrition.
Supportive measures that can be tried (effectiveness varies):
-
Lower the water level to 50–80 cm to reduce pressure.
-
Increase aeration and maintain stable water quality.
-
Stop feeding or provide small amounts of easily digestible feed.
-
Isolate the fish in a quiet environment to minimize stress.
Important reminder: Diving disease progresses slowly (weeks to months) and has a poor prognosis. Some keepers have tried antibiotics, anti‑inflammatories, or vitamins, but results are inconsistent. Blind use of medication is not recommended.
How to Distinguish It from Other Diseases
|
Disease
|
Key Distinguishing Features
|
|---|---|
|
Swim‑bladder disorder
|
Complete loss of balance; fish may roll over or float upside‑down, unable to swim normally.
|
|
Gill disease
|
Rapid breathing, gasping at the surface, but no repeated diving behavior.
|
|
Enteritis
|
Accompanied by white feces and loss of appetite, but swimming posture remains normal.
|
