Understanding Gas Bubble Disease in Seahorses-How to Treat and Prevent


Understanding Gas Bubble Disease in Seahorses-How to Treat and Prevent

With the proper setup and care one should not run into this problem with their seahorses. We wanted to create a helpful guide to help those experiencing these issues, help new keepers create a setup that is proper for their animals to prevent GBD issues, and perhaps give hobbyist ideas on how to improve their existing aquarium for their seahorses.

What is Gas Bubble Disease (GBD) in Seahorses?

It is important to note that Gas Bubble Disease is a term used to describe three symptoms seen in seahorses and not an actual disease. There are still a lot of unknowns about GBD in seahorses, and why some individuals will develop this while others do not. Typically GBD is environmentally triggered, meaning something is off in the aquarium that causes these symptoms to occur. 

The good news is since GBD is environmentally caused it is completely preventable as well. It is also not contagious to your other seahorses, but if one seahorse is showing symptoms of GBD your other seahorses in the aquarium could also develop this issue since it is environmentally triggered. 

Three Forms of Gas Bubble Disease

1. External Gas Bubble Disease

This is when there is subcutaneous (under the skin) gas is trapped outside of the body cavity. It is commonly seen on the tail or head but can be found anywhere on the body of the seahorse. This can occur in both male and female seahorses. 

The cause of external gas bubble disease could be from internal gas imbalances, secondary from bacterial issues under the skin releasing gases or other possible unknown causes.

2. Internal Gas Bubble Disease and/or Bloat

This is when there is swelling of the whole body and/or tail. Unfortunately when this occurs throughout the whole body severe internal damage often results from the swelling. If caught early the seahorse has a chance of recovering but if let go this is often fatal. This can be seen in both male and female seahorses.

3. Pouch Emphysema

This form of GBD is when a build up of gas is trapped in the male's broodpouch. When this occurs the male seahorses will have buoyancy issues causing him to float or struggle to stay upright when swimming. This only occurs in male seahorses since they have a broodpouch and female seahorses do not. If there is an internal imbalance of gas in the bloodstream of the seahorse it is very likely the male may develop a build up of gas in the broodpouch. Since the pouch is highly vascularized with a lot of blood flow the excess gas in the blood can easily escape to this open "pocket".

Pouch Emphysema-How to Preform a Pouch Evacuation

If you find your male seahorse floating, his pouch is enlarged, and there are no signs of external Gas Bubble Disease he is very likely to have gas trapped in his broodpouch. To provide him immediate relief you will want to preform a pouch evacuation. While this will provide him immediate relief it is important to troubleshoot and figure out what stressor is causing this symptom to occur.

It is important to familiarize yourself with where the broodpouch opening is located. If you do not have a catheter, the blunt end of a paper-clip or bobby pin can also work for this. Make sure that whatever instrument you use is sterile, washing with soap and hot water if need be. The pouch evacuation should be preformed under water. The seahorse should be gently held in one hand and use your other hand to preform the gas evacuation. You will tilt your male seahorse back at a 45 degree angle and use the catheter to gently open the broodpouch (see diagram above for where to find the broodpouch opening). Open the pouch only enough to let the trap gas escape. Manipulate the pouch with your finger and move the seahorse to allow the gas to escape. It is extremely important to NOT squeeze the gas out of the pouch as this will lead to injury of your seahorse! 

Below is a helpful video on how to preform a pouch evacuation on a male seahorse.


While sometimes this is a one off occurrence, be prepared to need to preform more than one pouch evacuation. Since Pouch Emphysema is often a symptom of an internal gas imbalance it often will reoccur until the stressor is reversed. Even if you figure out what the stessor is, it can take time for the seahorse to sort itself out and the process causing the internal gas imbalance to correct itself. One should preform a pouch evacuation no more than once daily.

Can Pouch Emphysema Occur in Pregnant Male Seahorses?

While very uncommon, pregnant males can sometimes develop gas in the broodpouch from embryos not developing correctly, passing and fouling in the broodpouch. This is not a form of GBD but can it occur. If you preform a pouch evacuation and find your male seahorses is pregnant this may be what has occurred and evacuating the pouch should fix this issue. Unfortunately the brood will likely be lost. Seahorses are prolific and they will likely have another batch again. Environmental stressors may not be a factor in this situation.

Pregnant males can also develop GBD so it may be difficult in this situation to know exactly what the cause is. 

How to Setup a Hospital Tank and Treat Your Seahorse for Gas Bubble Disease

It is important to remember GBD is environmentally triggered. One should absolutely troubleshoot and figure out what is the cause of these symptoms in their aquarium. Typically if you can figure out the cause(s) and fix these the symptoms of GBD will reverse on it's own with time.

Using Diamox (Acetazolamide) to Treat Gas Bubble Disease

Severe cases of GBD may require treatment using Acetazolamide, brand name Diamox, a carbonic anhydrase inhibitor to be reversed. This treatment must be done in a separate hospital tank. This drug is often used to treat glaucoma, epilepsy, altitude sickness, and more in humans. Since this is a prescription drug one must have their veterinarian prescribe this for them. Most veterinarians are not familiar with seahorses specifically and for this reason it can be difficult to get them to write a prescription for your seahorse. Some vets by law have to see the animal before they can write a prescription for it.

In our experience it helps to bring in documentation to the vet's office such as this article, a treatment plan, and a photo of your sick seahorse. Usually if you can show the veterinarian why you need the medication for your seahorse they will work with you.

If you are not able to obtain this prescription from your veterinarian it still may help to move your seahorse to a hospital tank with new saltwater. Since GBD is environmentally triggered moving your seahorse to better water quality can often reverse the issue without medication. One will still want to troubleshoot to figure out what is off in the display tank to prevent re-occurrence of this problem.

Setting up the Hospital Tank

A 10 gallon hospital tank generally works well for this. A Hang-on-Back filter to add water circulation is all that is needed. NO chemical filtration (carbon, ect) in the hospital tank. A heater typically is not necessary and keeping the treatment tank on the cooler side (68-70 F) is ideal. If you do find you need a heater, you will need to add a heater cover or your seahorse can get burned if it hitches to the heater. Heater guards can be found on Amazon or you may be able to make one yourself. No biological filtration in the hospital tank. Fill the hospital tank with newly mixed saltwater (not your aquarium water) that matches the specific gravity and temperature of your aquarium. No sand or liverock in your hospital tank, it needs to be completely bare-bottom. Artificial hitching-posts for your seahorse to hold onto is a must. Lighting should be minimum during treatment to reduce stress.

Treatment-Diamox Bath

You will dose your 10 gallon hospital aquarium with one 250 mg tablet dissolved to prepare a Diamox (Acetazolamide) bath at 25 mg per gallon. To dissolve the pill it may help to blend it in the blender with saltwater. Daily 100% water changes are required and you will dose the hospital aquarium daily after the water change until the symptoms have resolved. It is important to make sure the temperature and salinity of the new water matches when doing a water change. Treatment is typically 8 days or until this problem has been resolved. Diamox (Acetazolamide) is very effective at treating Gas Bubble Disease with seahorses.

Treatment-Diamox Flush 

In some cases of GBD in male seahorses it may be more effective to administer Diamox via a pouch-flush. Since the the broodpouch is highly vascularized the medication can quickly be taken into the bloodstream and be more effective this way.


Thoroughly blend (literally in a blender) 1/4 of a 250 mg Diamox tablet in 1 cup of newly mixed saltwater. The saltwater should match the specific gravity and temperature of the aquarium. When blending Diamox it typically never 100% dissolves and residual is often seen. You will want to allow the residuals to sink to the bottom, do not introduce solids into the male's pouch. Use a 0.5-1 mL syringe attached to a gauge or catheter to administer ~0.5 mL of the solution into the broodpouch opening. This can be done once daily until symptoms have resolved. 

Side Effects of Acetazolamide on Seahorses 

Diamox (Acetazolamide) has a side effect of loss of appetite and tends to make them less active. You may need to offer live foods such as adult-sized Artemia (brine shrimp) and/or live Mysis shrimp if you have difficulty getting your seahorse to eat during treatment.

Secondary Bacterial infections with GBD

Unfortunately secondary bacterial related infections can occur with GBD. The trauma from the skin inflammation as well as stress can make the seahorse susceptible to bacterial infections. External gas bubble disease can even sometimes possibly be caused from a bacterial related issues under the skin. If the gas bubble has discoloration there may be infection as well. There is really no way to know with certainty without a biopsy. Since most keepers do not have access to do a biopsy on their seahorse and being quick to treatment is key, you may consider adding an antibiotic such as Furan 2 (Nitrofurazon) in addition to Diamox.

If there is no discoloration or suspected bacterial infection we recommend only treating with Diamox (Acetazolamide). Using an antibiotic unnecessarily is not only adding stress but can create antibiotic resistance. In short, this could cause more harm and is only recommended as needed. Furan 2 (Nitrofurazon) and Diamox (Acetazolamide) have been used together at the recommend dosages without observed side effects. 


Troubleshooting-Possible Causes and Ways to Avoid Gas Bubble Disease

Reduce Organics!!!

Reduce dissolved and non-dissolved organic matter (waste) in your aquarium! We find too much organic waste to be one of the most common issues leading to GBD!

-Having a build up of detritus in the system will lead to these issues. Excess detritus creates an environment for "nasty" bacterial which will stress your seahorses. When present in large amounts the decomposition process of this waste can also lower pH causing imbalance in your aquarium. 

-Avoid crushed coral substrate and other large particle substrates. Large particle sized substrates have large void areas between the particles which allows for waste to settle down into the substrate. If the use of sand is desired we recommend fine aragonite sand in the ~0.5-1.5 mm range, "Fiji Pink" is a easily available substrate that we like. The substrate layer should be less than 1" in depth. The most hygienic option is "Bare Bottom" which is no substrate at all. The (outside) bottom of the aquarium can be painted, or a piece of "Star Board" marine-grade cutting board can be purchased and cut-to-fit on the bottom inside of the aquarium. "Starboard" will prevent the reflective view of the bare aquarium bottom.

-Increase your water flow. Too low of water flow can also allow for build up of organics. Ideal water flow, when combined with a bare bottom aquarium, will all detritus to remain in suspension until it is removed by the mechanical filtration.

-Lack of a good protein skimmer will cause issues with high organics. 

-Do more frequent partial water changes. 10% of the aquarium volume per week is a good baseline to begin with, adjusting as needed.

-Use activated carbon to help remove dissolved organics. Change it often, every 2-4 weeks is recommended.

-Do not overstock your aquarium.

-Change your filter socks (or other mechanical filtration) often. We change our filter socks daily at our farm. We do not recommend going more than 2-3 days for changing socks on a seahorse aquarium. Remember mechanical filtration does not remove solid waste from the aquarium system, it gathers it in one spot for you to more easily remove!

-Do not allow detritus to build up in the sump, canister filter, under the rockwork, ect. If you find a build up of detritus it is best to siphon it out rather than stir it up in the aquarium! 

-Do not leave uneaten food in the aquarium for longer than 30 minutes, like any seafood, frozen Mysis shrimp will quickly begin to spoil.

-Having a UV sterilizer can also help breakdown organics as well as reduce bacteria, algae, some parasites and other benefits. We love using them on our seahorse systems! 

Maintain High Water Quality

-Again, be careful to not over feed, leftover food will deteriorate your water quality.

-Maintain a good clean-up crew in your aquarium (blue leg hermits, Nassarius snails, Cerith snails, Margarita snails, and small serpent stars are great clean-up crew for a seahorse aquarium).

-Regularly check your water parameters including pH, specific gravity, temperature, phosphates, nitrates, nitrites and ammonia.

-Preform water changes often. Every system is a different but 10% of the aquarium volume per week is a good baseline to begin with, adjusting as needed. Some systems may require larger water changes.

-Change your chemical filtration (carbon, GFO, ect) often. We recommend changing your carbon and/or GFO every 2-4 weeks.

-Always use RODI or distilled water for top-off and making saltwater for water changes. We do not recommend using tap water, well water or bottled water. There are too many unknowns with these water sources. 

-We highly recommend having a good quality, over-sized protein skimmer to remove waste. The brand of protein skimmers found at the big-box pet store are not efficient and productive units. Contact us for help in choosing the correct protein skimmer for your system. The protein skimmer is sort of like the kidneys of the aquarium, you want it to do a good job.

-High nitrates, high phosphates, high organics, and any detectable ammonia and nitrite can be stressors contributing to symptoms of GBD. 

-Make sure you have plenty of media for beneficial nitrifying bacteria to populate! We really like MarinePure media for increasing the surface area for these beneficial bacterial. The spheres or if you have the space for the large blocks are our favorites! These ideally should be placed in a sump but you can place them in the aquarium or hang on the back filter. We MarinePure media in every system at our farm and have since we started over 5 years ago. We love it!

Reduce Stress

Stress can possibly lead to changes in the blood chemistry of your seahorses (acidosis) which can cause an internal gas imbalance. Stress is very unhealthy in general and can make your seahorses more susceptible to other issues. It is very important to reduce stress.

-Do not over stock your aquarium. 

-Avoid aggressive tank-mates.

-Make sure there is no stray voltage with your equipment.

-Keep the aquarium stable (temperature, water parameters, ect).

-Reduce vibrations from unlevel or old pumps.

-Keeping your aquarium temperature between 70-74 F for species other than cold-water species. Higher temperatures often leads to higher bacterial counts. Some strains such as Vibrio spp. grow exponentially with warmer temperatures. Seahorses are more prone to bacterial related issues compared to most other fish as they have a primitive immune system. Exposing them to these bacteria not only makes them more susceptible to bacterial related issues but it works their immune system harder and therefore is a stressor. The use of probiotics in your aquarium can also help reduce stress by allowing these non-harmful strains of bacteria to out-complete some of these "nasty" possible harmful bacterial strains.

Maintaining Good Gas Exchange on Your Aquarium

-Water flow-Make sure you have moderate to slightly high water flow. Every system is a little different in how much water flow makes for a healthy system. To give you a general idea on what to aim for we recommend at least 10-25 turnover of tank volume per hour. Low water flow is NOT recommended! This will create poor gas exchange and not allow as much filtration to occur.

-Surface agitation: It is important to have surface agitation, water movement at the surface, in your aquarium. This allows for better gas exchange, and will often help keep your aquarium cooler as well due to evaporative-cooling. 

-Open Top Aquarium-It is helpful to have an open top (no hood) on your seahorse aquarium if possible. Having a hood can trap CO2 in the aquarium and create low pH which can lead to GBD. A hood can also trap heat which will make it more challenging to keep your aquarium cool. If you need a cover to keep fish from jumping we recommend a mesh or egg crate lid. This is especially important in the summer months when they house is more closed up and the AC is on. Not having a lot of air exchange in the house itself can also create higher levels of CO2.


There are still a lot of unknowns in the scientific community and many theories about what is happening internally when a seahorse shows GBD symptoms. The process of acidosis is certainly a possibility in some cases.

What is Acidosis

Acidosis is when the body fluids are too acidic. In fish respiration via the gills, and the kidneys, maintain blood pH. Acidosis can occur when blood becomes too acidic. When this occurs excess protons in the bloodstream can cause carbonic anhydrase emzymes (emzymes that help regulate the blood pH) to produce CO2 gas from carbonic acid. When this process occurs it could lead to too much gas in the system, which can lead to embolisms and eventually into the symptoms of GBD we see in seahorses. In simpler terms, too low blood pH can possibly lead to internal gas imbalances.

How Can Acidosis Occur

Acidosis in seahorses could be triggered when the pH is too low in the aquarium and/or can be stress induced. For this reason it is very important to reduce stress in the environment to prevent this possibility.

If the pH in your aquarium is too low, it is important to not jump the gun and quickly dose to raise the pH. Quick changes in pH can also cause stress, imbalances, and therefore possibly lead to these symptoms as well. We have seen these symptoms occur from dosing for pH, calcium, alkalinity (kalkwasser and two-part additives) in both our own systems and when troubleshooting with customers over the years. If you have low pH in your aquarium one will have better success at doing more frequent water changes and troubleshooting to figure out why the pH is low, rather than dosing, to fix this issue. Healthy aquariums with only soft corals, getting regular water changes, should not have low pH issues unless some other factor is at play (such as poor gas exchange).

GBD Misconceptions!!

While we have gone over the ways to prevent GBD we feel it is important to bring up some of the common misconceptions and "old school" thoughts we often see and hear. 

  • Protein skimmers lead to over-saturation of oxygen in the water. While this is possible to occur, it is very unlikely to be the issue causing GBD. We highly recommend having a protein skimmer on your seahorse aquarium and use them on every system at our farm. A protein skimmer helps pull out organic waste and therefore improves your water quality in the aquarium. It can also help reduce nitrates by removing organic compounds before they have a chance to break down and release nitrogen compounds. Protein skimmers pull air in and help add oxygen to the water which are all good things and can help create better gas exchange in your aquarium. The benefits of improved water quality by having a protein skimmer far outweigh the unlikely chance of over saturation of gas in the water. 
  • Only male seahorses develop GBD. It is true only male seahorses develop pouch emphysema (PE), a form of gas bubble disease. Females do not develop PE as they do not have a broodpouch. With that said, the same environmental stressors leading to PE in male seahorses can lead to other forms of GBD in female seahorses such as Internal and External GBD. With a proper setup one should not have concerns about GBD.
  • Seahorses develop GBD from ingesting air bubbles or air bubbles getting trapped in the male broodpouch. It is very unlikely for a seahorse to ingest air and for this to cause a buoyancy issue. A healthy seahorse will often release any snicked air on its own or pass it with no issues. While it is possible for a male seahorses to get air trapped in his broodpouch while courting he can often expel this on his own with no issues.
  • Having an airline/bubbler in your aquarium will cause GBD. Having an airline in your aquarium will not lead to over-saturation of oxygen and therefore GBD in your seahorse aquarium. The bubbles put off by most airlines are too large to cause any saturation issues. This can actually help some aquariums with better gas exchange by adding fresh air into the water and creating more surface agitation. We find many seahorses to really enjoy these and they will often hitch to the airline and "play" in the bubbles. It is very unlikely for this to cause air to get trapped in the males broodpouch as well.
  • A really tall aquarium is needed for seahorses or they can develop GBD issues. While you do not want your aquarium to be too small or too shallow this is not a cause of GBD. Seahorses are vertically oriented fish and most larger species kept in the home aquarium reach 5-8+ inches. You will want to make sure your seahorses have plenty of space when they reach maturity. We find horizontal space to be equally as important as vertical space. We recommend for the larger species having at least 18 inches height but don't cut your horizontal space short by picking out a taller aquarium! 
  • Lancing or popping the gas bubbles. This should NOT be done!!! This will cause open wounds which will make your seahorse much more susceptible to bacterial issues. Secondary bacterial issues can be as serious if not a bigger problem than the GBD itself. 


We hope you find this article helpful. Understanding GBD is complex and if you have any questions our staff is more than happy to help you. Feel free to reach out to us. We want you to be successful with keeping your seahorses. 

Email: alyssa@seahorsesavvy.com

Phone: 410-618-3604