Male seahorse and air in pouch

Dear Sherry:

I’m sorry to hear about the periodic problems your stallions have been having with pouch gas, Sherry, but that’s a common affliction for seahorses in the home aquarium.

There is no simple answer to your question about what causes gas to build up within the pouch of male seahorses, since that’s a rather complicated issue, but I’ll do my best to briefly explain what is happening when this problem occurs. The air does not actually get “into” the pouch of the stallion from elsewhere – rather, the gas is formed within the marsupium itself and continues to build up within the pouch until it becomes bloated and swollen and the seahorse is having problems with positive buoyancy (i.e., the tendency to float).

This condition is a form of gas bubble syndrome (GBS) and is commonly known as chronic pouch emphysema. Although GBS is virtually unknown at the Ocean Rider aquaculture facility, gas bubble syndrome in its various forms is probably the most common health problem for home aquarists who keep seahorses, Sherry.

That’s the bad news. The good news is that GBS is an environmental problem, rather than a disease process, and it is therefore entirely preventable. When it occurs, it is not at all contagious and does not spread from one seahorse to another. Females are rarely affected, since it is the physiologically dynamic brood pouch of the males that makes them susceptible to GBS, and mature males that are actively courting and breeding are especially vulnerable to chronic pouch emphysema, also known as bloated pouch or pouch bloat. Finally, when it does occur, most forms of GBS are easily treated and cured simply by evacuating the gas that builds up within the male’s pouch and then performing a pouch flush and administering acetazolamide (brand name Diamox), if you can obtain it.

In summation, the good news regarding GBS is that:

(1) it is not a disease and is entirely preventable.

(2) it is not at all contagious and is not spread from seahorse to seahorse.

(3) female seahorses are largely immune to such problems and are very rarely affected by GBS.

(4) males can be easily cured in most cases by performing a thorough pouch flush and treating them with antibiotics in conjunction with Diamox.

The best ways for the home hobbyist to prevent GBS are to use a reasonably tall aquarium, maintain optimum water quality at all times, reduce the organic loading in the aquarium as much as possible, make sure your seahorse tank has excellent surface agitation and aeration to promote efficient gas exchange at the air/water interface, and to keep the substrate of the aquarium clean and sanitary, Sherry.

In general, anything you can do to improve the water quality and reduce the organic loading in your aquarium will help minimize problems with GBS. Improving the surface agitation and aeration to facilitate better gas exchange and offgassing at the air/water interface is a good place to start, since that will help to eliminate any potential problems with low-level gas supersaturation of the aquarium water, which is one of the environmental triggers that causes problems with GBS. It will also help to stabilize the aquarium pH by keeping the levels of dissolved oxygen high and the levels of dissolved carbon dioxide low, which will be very beneficial in the long run. Likewise, anything you can do to provide your seahorses with a stress-free environment will be helpful in preventing such problems in the future.

In my experience, most home hobbyists do very well in that regard for the first 4-6 months that their seahorse tank has been up and running, and they typically have no health problems during this time. Eventually, though, over the months they become a little more lax about cleaning up leftovers promptly, performing regular water changes and conducting routine aquarium maintenance, and organic wastes begin to build up in the aquarium as a result. Sooner or later, this begins to affect the water quality and the pH of the aquarium gradually drops while the nitrate levels steadily rise, until all of a sudden one of the male seahorses develops a problem with pouch gas (pouch emphysema) or tail bubbles (subcutaneous emphysema). Typically, those are conditions that are easily resolved by burping the pouch and/or performing a thorough pouch flush and then treating the seahorse with Diamox, after which the stallion is good as new again.

However, if the hobbyist does not correct the water quality issues and heavy organic loading that has accumulated in the aquarium, and does not make sure that gas supersaturation is not occurring, and thus fails to address the underlying cause of the GBS, other problems with GBS will begin to crop up from time to time thereafter.

This is what I usually advise home hobbyists regarding GBS, Sherry:

Gas bubble syndrome (GBS) is a mysterious, widely misunderstood affliction that can take on many different incarnations. As you know, gas bubble syndrome is believed to be caused by gas emboli forming within the tissue of heavily vascularized portions of the seahorse’s anatomy — the placenta-like brood pouch of males, the eye, the muscular prehensile tail — and it can take several different forms depending on where the bubbles or emboli occur. When it occurs in the brood pouch of the male, chronic pouch emphysema or bloated pouch results, leading to positive buoyancy. (Chronic pouch emphysema is by far the most common form of GBS and is, of course, restricted to males only.) When it occurs in the capillary network behind the eye (choroid rete), Exopthalmus or Popeye results, and the eye(s) can become enormously swollen. When it affects the capillary network of the gas bladder (the rete mirabile), hyperinflation of the swimbladder occurs, again resulting in positive buoyancy. When it affects the tail or snout, external gas bubbles (i.e., subcutaneous emphysema) form just beneath the skin and look like raised blisters. When intravascular emboli occur deep within the tissue and occlude blood flow, generalized edema results in the affected area. Or extravascular emboli may cause gas to build up within the coelom, often resulting in positive buoyancy and swelling or bloating of the abdominal cavity (internal GBS).

Different parts of the body can thus be affected depending on how the initial gas emboli or micronuclei form, grow and spread.

The mechanisms by which the gas emboli can spread and grow, and the type of insults that can result are therefore fairly well known, but the etiology of GBS is otherwise still poorly understood, and there are many theories as to what causes the gas embolisms to form in the first place. Nitrogen gas supersaturation of the water, the unique physiology of the male’s brood pouch, malfunctions of the pseudobranch or the gas gland of the swim bladder, stress-related changes in blood chemistry that affect the oxygen-carrying capacity of hemoglobin, excess organics (dissolved organic compounds and organic wastes) leading to unsanitary conditions in the seahorse tank, infection with gas-producing bacteria — all these and more have been advanced as mechanisms that could trigger the formation of the gas embolisms at some point. Very likely GBS has multiple causes, but most experts now believe it is due to physical conditions in the seahorse tank rather than any sort of pathogen.

In short, it’s very unlikely that any sort of disease organisms or pathogen causes GBS. It is not at all contagious and does not appear to spread from seahorse to seahorse. To my knowledge, no one has ever been able to isolate a pathogen from the marsupium of the male with pouch emphysema or from the subcutaneous emphysema that characterize seahorses with tail bubbles. If bacteria play a role in GBS, I am confident it is only as a secondary infection.

In other words, gas bubble syndrome is not a disease that seahorses contract after being exposed to a pathogen of some sort, but they will often develop the condition when kept in a system that exposes them to gas supersaturation, insufficient water depth, stress, inadequate water circulation, heavy organic loading, a bacteria-laden substrate or other environmental factors conducive to the formation of gas emboli. In other words, it is an environmental disease, triggered by certain conditions within the aquarium itself. In my experience, the environmental triggers that are most often associated with GBS are as follows:

1) Insufficient depth (aquaria that are less than 20 inches deep are very susceptible to GBS, and the taller the aquarium is, the more resistant it will be to GBS). This is because of the greater hydrostatic pressure at depth in tall tanks, which can actually cause gas emboli to go back into solution. (Indeed, most forms of GBS can be resolved simply by immersing the affected seahorse at a depth great enough to cause this to happen.)

2) Gas supersaturation of the aquarium water, which can lead directly to the formation of gas emboli within the blood and tissues of seahorses. (Increasing the surface agitation and aeration in the aquarium to promote better offgassing and more efficient gas exchange will help to eliminate potential problems with gas supersaturation.)

3) Changes in the seahorse’s blood chemistry (i.e., acidosis). Anything that tends to acidify the blood of the seahorses can result in GBS, including stress, low levels of dissolved oxygen and/or high levels of CO2, and low pH in the aquarium water, among other factors.

Okay, Sherry, that’s the quick rundown on GBS in seahorses. It is a very common problem for home hobbyists who are having water quality problems, but it is easily prevented in a well-maintained aquarium.

Just maintain good water quality, don’t overfeed and remove uneaten leftovers promptly, maintain good surface agitation and aeration in the aquarium at all times, provide your ponies with a stress-free environment, and reduce the organic loading in the aquarium as much as possible. One very simple and effective way to help reduce the organic loading in a seahorse tank is to add a booster of AquaBella BioEnzyme Water Treatment System for saltwater or to dose the tank with Seachem Stability once a month.

Burping the pouch to release the trapped gas as you have been doing will provide the stallion with immediately relief, Sherry, but most of the time the relief is only temporary because more gas will soon begin accumulating within the pony’s pouch, resulting in positive buoyancy, and the problem will recur.

That happens because burping the pouch does not address the underlying problem that is causing the gas to build up within the pony’s pouch to begin with, so you can expect the problem to be return as more gas gradually accumulates within the stallion’s marsupium. When that is the case, you cannot simply continue to burp the pouch to deal with the situation. Repeatedly burping the pouch is not a long-term solution for this problem and it will eventually result in serious pouch infections that often prove fatal.

In other words, Sherry, burping or manually evacuating the excess gas from a male’s pouch when he is having problems with positive buoyancy can certainly provide him with some immediate relief, but when you have to repeat the procedure for manually evacuating gas from a seahorse’s pouch more than once, it becomes increasingly hard on the seahorse and will not resolve the problem once and for all because you are merely treating the symptoms and not the cause of the gas build up.

When that’s the case, Sherry, you need to move on to more aggressive forms of treatment in order to resolve the problem with chronic pouch emphysema once and for all. The next time you are faced with this problem, go ahead and evacuate the gas from the male’s pouch as usual, but then perform a thorough pouch flush afterwards.

In the meantime, be sure to make some changes in your aquarium system to improve the water quality and lower the organic loading in the tank, as well as increasing the surface agitation and aeration to eliminate low-level gas supersaturation as a potential cause for the problem.

If the chronic pouch emphysema should occur yet again, you will need to evacuate the trapped gas and then perform a medicated pouch flush using antibiotics and/or Diamox, if you are able to obtain it (Diamox is a prescription medication that is often difficult for the home hobbyist to acquire). And you will need to continue to work on the aquarium conditions to eliminate as many of the environmental triggers for GBS as possible.

Otherwise, Sherry, repeatedly evacuating the air from the male’s pouch is counterproductive in most cases because the constant manipulation can be hard on the tissue of the pouch, aggravating the dermal layers of the marsupium and leaving them vulnerable to secondary infections. (The male marsupium is far more complex than most hobbyists realize, consisting of four separate layers of epithelial and connective tissue, with the innermost layers being heavily vascularized.)

The skin or integument of the pouch is of course its first line of defense against disease. It contains mucus glands, and the slime covering the skin acts as a barrier to ectoparasites and infection. The protective slime may even contain antibodies and antibacterial substances (Evans, 1998). Marine fish are always in danger of dehydration because the seawater they live in is saltier than their blood and internal body fluids (Kollman, 1998). As a result, they are constantly losing water by diffusion through their gills and the surface of their skin, as well as in their urine (Kollman, 1998). The mucus layer also acts as a barrier against this, waterproofing the skin and reducing the amount of water that can diffuse through its surface (Kollman, 1998).

Repeatedly burping or massaging the pouch removes this protective barrier, and the shearing pressures that are involved may aggravate the underlying tissue, resulting in secondary infections of the outer marsupium that can further complicate the picture.
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Let me know if it would be helpful for me to provide you with some directions for flushing the pouch of the affected seahorses, Sherry, and for performing a medicated pouch flush, if necessary.

In the meantime, if you contact me via e-mail, I can provide you with some much more detailed suggestions for preventing GBS. I have a large file on this subject I can send you that explains the mechanisms responsible for gas bubble syndrome in more detail, as well as discussing a number of modifications you can make to the aquarium to minimize problems with GBS in the future, but it includes way too much information for me to post it on this forum.

You can reach me at the following e-mail address at any time:

[email protected]

Best of luck resolving this problem once and for all, Sherry.

Respectfully,
Pete Giwojna, Ocean Rider Tech Support