Gas Bubble Disease:

What the heck is it?

By Will Wooten

What is gas bubble disease? If you're unfamiliar with it and just happen to be browsing this website, you may be completely clueless on the issue. There are three general conditions that may be described as gas bubble disease: internal gas bubble disease, external gas bubble disease, and pouch emphysema. So, what exactly are they?

External Gas Bubble Disease

External gas bubble disease (EGBD) is thought to be caused by either bacterial infection (wherein waste CO2 produced by the infecting bacteria becomes trapped underneath the skin) or by gas super-saturation of the water in which the seahorses reside. Gas super-saturation causes problems similar to the bends, which affects SCUBA divers. The situation, wherein gas levels in the water are much higher than normally possible (caused by limited areas for gas escape), causes gas bubbles to form anywhere possible. Because the pressure inside of a seahorse is lower than the pressure of gas super-saturated water, the gas bubbles emerge directly under the skin of the affected seahorse. Since the air bubbles cannot pass through the skin, they remain stranded there until treated or until they can be reabsorbed by the seahorse's own body.


  • subcutaneous (under the skin) air bubbles that may occur anywhere on the head, body, or prehensile tail
  • buoyancy and movement complications

The bubbles can cause stress on a seahorse as problems with buoyancy and movement arise. If left unchecked, the disease may eventually cause death in the infected specimen due to this stress. The appearance of external gas bubble disease can be a sign of more serious problems. Possibly significant, EGBD is common more in wild-caught seahorses than in captive-bred seahorses. This may be due to a difference in pressure between deeper ocean habitats and relatively shallow aquariums. At Chicago's Shedd Aquarium, all specimens of one species kept in tanks shallower than three feet soon succumbed to EGBD.

External gas bubble disease can manifest itself anywhere on a seahorse's body. It often appears on angular areas of the body such as spines or between the sides and back.


Often, external gas bubble disease occurs on the tail of afflicted seahorses. Some anecdotal evidence suggests that only male seahorses can be affected on the tail.
Advanced cases of internal gas bubble disease usually damage internal organs to the point of no return. Unfortunately, there is little that can be done at this point.

Internal Gas Bubble Disease

The possible causes of internal gas bubble disease are a constant topic of conversation and argument. It is thought to be caused by some of the same factors as external gas bubble disease-- gas super-saturation or advanced bacterial infection --although its precise cause is unknown. Unfortunately, if given the opportunity to progress to actual total-body bloating, it is often too late for the infected seahorse to recover.


  • severe bloating of the entire body
  • external gas bubbles
  • exophthalmia
  • extreme buoyancy and movement complications

The most grave problems with internal gas bubble disease lie in its crippling effects on the infected specimen's internal organs. If allowed to progress, often the organs are damaged beyond recovering, leading to severe organ failure. If the condition can be detected before reaching such an advanced stage, the prognosis is exponentially better. Usually early stages of internal gas bubble disease can be reversed using carbonic anhydrase drugs such as acetazolimide.

Pouch Emphysema

As with internal and external gas bubble disease, the causes of pouch emphysema are highly disputed within the seahorse hobby. It was once thought that the condition could be traced to embryonic that is not expelled during labour rotting inside of the pouch. This decomposition process would yield gasses that inflate the pouch. Due to the fact that the condition often shows up in 'virgin' male seahorses, however, other theorized causes may be more reasonable. These theories include micro-bubbles in the water column that can collect in the pouch during mating rituals and bacterial infections, the waste products of which include gases that can fill the pouch. This type of infection is often attributed to recurring pouch emphysema.

More recent research, however, has traced a more likely cause to a biological process known as the hydration of CO2(g), carbon dioxide gas, to H2CO3(aq), carbonic acid. This process occurs on a cellular level. An enzyme known as carbonic anhydrase catalyzes the hydration of CO2(g) with H2O(l) to H2CO3(aq), carbonic acid. When this reaction is disturbed, however, CO2(g) is not converted into H2CO3(aq), thus leading to a buildup of carbon dioxide gas in the pouch tissues. The exact cause of the disruption of this process, however, remains unknown. In humans, stress can catalyze this type of problem, so stress may be a cause in seahorse gas imbalances.


  • grossly bloated/swollen pouch
  • severely hindered locomotion and
  • buoyancy problems

This malady only infects male seahorses as females do not have pouches. If not treated, the condition will cause the infected male to have limited locomotion and severe buoyancy problems that can lead to stress and secondary infection. Cessation of appetite normally follows, and the horse may starve. Other problems include the possibility of the infected horse becoming stranded on a filter intake, overflow box, or similar piece of equipment. Prolonged experiences like this can cause internal injury and stress.

External gas bubble disease can manifest itself anywhere on a seahorse's body. It often appears on angular areas of the body such as spines or between the sides and back.


In most cases, pouch emphysema can be cured with a simple pouch evacuation. >>View article on pouch evacuations

Most recent revision: 2003

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