Gas Bubble Disease: Etiology, Pathology, Diagnosis & Treatment


A noninfectious condition associated with the supersaturation of dissolved gases, most commonly nitrogen or oxygen, in the water column causing bubbles to form in the eyes and other tissues of the fish.
Gas Bubble Disease


Numerous etiologies are known to cause supersaturation of gases within the water column including leaks in pumps, valves or pipe connections; overaeration of water; sudden extreme temperature gradients; heavy algal blooms; use of spring or well water that has not been sufficiently degassed; and being in close proximity to plunge pools of dams or waterfalls where increased levels of dissolved gases may occur in the water column.

Route of Transmission

Not applicable.

Host Range

The condition has been reported in numerous farmed, aquarium, and wild fish species, though syngnathids (i.e., seahorses and pipefishes) in captivity appear to be more sensitive to increased gas saturation conditions.
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Clinical Presentation

Clinical signs and mortality vary with species, age, and degree and duration of gas supersaturation. Fish can be affected by acutely or chronically increased levels of gas saturation that manifest in a variety of clinical signs including air bubbles in the anterior chamber of the eye, air emboli in the capillaries of the gills and tissues, and dermal bulla in the skin and fins.


Retrobulbar gas bubbles can push the globe forward causing exophthalmos, which can result in keratitis, uveitis, panophthalmitis, and cataract formation. Supersaturation of the water can cause emboli to accumulate in the anterior chamber, vasculature, and adnexal structures of the eye.

Differential Diagnosis

Though the condition is fairly straightforward to diagnose, the cause can often be difficult to determine.


Most commonly diagnosed by visual inspection of the eyes, gills and skin for the presence of gas bubbles in the anterior chamber of the globe of the eye (or in the lamellae of the gill or under the epithelium of the skin).
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Management / Control

Depending on the length of time and the severity of the pathology, the lesions may regress once the cause and/or elevated gas levels are removed. Peribulbar injection of a carbonic anhydrase inhibitor (6 mg/kg acetazolamide) may help resolve gas bubbles within the choroidal gland and anterior chamber. Regular monitoring of water for dissolved gas levels is accomplished with a saturometer that measures differences in total dissolved gas between the atmosphere and water. It must be remembered that even though it might take saturation levels of 104%–110% for overt clinical signs to appear depending on the species involved, levels above 100% even without clinical signs can be chronically stressful to fish.

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