Swim Bladder Disease in Fish

Other than constipated goldfish, “swim bladder disease” is a very common home diagnosis. Or the more common vernacular, “My fish has swim bladder.”

Well, almost all pet fish species have swim bladders, so that fact is correct, but it is not a disease. “Swim bladder disease” is most common in goldfish and koi, with a high percentage in fancy varieties of goldfish. For 99% of koi, poor water quality is the cause of swim bladder disease. I have had one case of actual swim bladder disease in ONE case, shown below.

For this koi, her swim bladder is full of an sterile, non-cellular fluid. We don’t know why this happened, but it causes her to scoot around on her belly. But this is our ONE case of an actual swim bladder issue in a koi. We have had two instances of koi with tertiary swim bladders, but not causing any clinical signs.

For goldfish, 90% of our “swim bladder” cases are lethargy secondary to poor water quality. Most of our actual swim bladder cases are fancy goldfish with most likely structural deficiencies. We’ve illustrated this point previously with our case on red moor, Huxley. Compare this comet x-ray below…

To these fancy goldfish…

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Goldfish are supposed to have a two chambered swim bladder, but due to their anatomy, these fancy varieties have limited space in their coelomic cavities. This sets them up for buoyancy issues from birth.

Goldfish and koi are also physostomous fish, meaning that they inflate their swim bladders by having a pneumatic duct between their esophagus and swim bladder. When they eat at the surface, it encourages air to enter the swim bladder. This is the main reason we see swim bladder issues. Goldfish are prone to positive buoyancy disorders because they are voracious eaters, sucking in lots of air at feeding time.

Fish with negative buoyancy may not have enough room in their body to support a larger swim bladder. However, being negatively buoyant is much safer than positively buoyant. Air ulcerations can occur when a fish is stuck at the surface for extended periods of time. This occurs where the skin starts to break down by being exposed to long periods of air.

What To Do and NOT To Do

External floats, such as those praised on YouTube, must be designed with the fish’s external surface in mind. Anything that rubs up against the skin will disrupt the protective mucus coat and cause secondary infection. Any float attachment will be TEMPORARY. We only apply them to get fish the surface to naturally inflate their swim bladder. We can take air out surgically, but we cannot add it in case the swim bladder ruptures.

If your fish is showing signs of negative or positive buoyancy, CHECK YOUR WATER QUALITY FIRST. Only 10% of our goldfish cases are primary issues concerning the swim bladder. The other 90% are water quality, diet, maintenance or bullying/trauma. Do NOT add a float without proper surgical prep in order to minimize infection.