Why Is Your Fish Gasping For Air?

Fish gasping at surface

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Fish gasping for air at the surface of their aquarium or pond is a serious problem for all pet fish owners. This is a sign that your fish cannot breathe properly and is looking for the water with the highest oxygen concentration, which is the surface water. You may see fish congregating around the filter outflow or by the waterfall, other areas of high oxygen content. There are many potential causes behind your fish gasping for air and the sooner you figure out the cause, the faster your fish will recover and be less likely to die.

Why Do Fish Gasp for Air?

“Gasping” or "piping" is the term for when your fish is rapidly breathing at the water surface, often with part of their mouth above the surface. This is most often a sign that your fish isn’t getting enough oxygen. There are many reasons your fish may not be getting enough oxygen, both in the external environment and within the fish’s body. Below are the main reasons for this behavior.

Inadequate Filtration

All fish should be kept in an appropriately sized aquarium with a full-function filter, bettas included. If you see fish gasping at the surface of the water, check your filtration system first to make sure it is working properly and of adequate size for your fish. Depending on the shape and size of your aquarium or pond, relying solely on air diffusion across the surface of the water is not sufficient for most pet fish species. Water movement throughout the aquarium or pond is required to provide proper aeration. Filtration not only can provide oxygen to the water, but also supports nitrogen cycling, breaking down toxic ammonia into safer compounds.


Fish kept in crowded conditions can use up the dissolved oxygen in the water faster than it can be replaced. This is especially a concern in outdoor ponds in the summer, as warmer water holds less dissolved oxygen. At night, plants in the water, including algae, also use oxygen, making the dissolved oxygen levels lowest in the morning before sunrise. Reducing the number of fish and removing algae will help maintain higher oxygen levels in a pond.

New Tank Syndrome

When all new aquariums are started, the filtration will go through a nitrogen cycling process called "New Tank Syndrome." This is the process where beneficial bacteria colonize your filter and convert ammonia to safer products. During this process, the water will go through spikes in ammonia, nitrite and nitrate levels. If high enough, these spikes can seriously impair and even kill your fish. Be sure to add fish gradually over a period of weeks into a new aquarium so that the beneficial bacteria in the biofilter have time to grow and keep up with the fish waste that is being produced. Adding too many fish too soon will usually result in New Tank Syndrome and the high ammonia levels will damage the fish's gills and can kill them.

Brown Blood Disease/Methemoglobinemia

The middle stage of the nitrogen cycle is the conversion of ammonia into nitrite. If a high nitrite level persists, it can cause brown blood disease, or methemoglobinemia. In this disease process, nitrite binds with hemoglobin in the blood, kicking off oxygen. No matter how much oxygen you add to the water, it will not get into your fish’s body tissues, causing death by asphyxiation. It is very easy to test for this disease by measuring the nitrite level using a standard test kit.

Gill Damage

Your fish’s gills can be damaged due to many disease processes. Since they are exposed to the water, they can also be contaminated by debris and other toxins in the water, such as heavy metals, ammonia and chlorine. No matter how much oxygen is in the water, damaged gills will not be able to function properly and your fish will be seen gasping at the surface.

Gill damage can also occur with viral disease, such as Koi Herpes Virus and Carp Edema Virus. These viruses specifically target the gills and can make your fish act lethargic or die suddenly in addition to gasping at the surface. There are no treatments for any fish viral diseases other than supportive care. Depending on the virus present in your pond, your veterinarian may need to contact state officials to report certain diseases.

Parasites that replicate in the gills, such as White Spot or Dactylogyrus spp., can also cause gasping due to gill damage. You may see other signs of irritation, such as flashing, decreased appetite
and lethargy. There is no one treatment for all parasites, so resist dumping in a bunch of drugs. Aquatic parasites often enter a clean system through a new, infested fish. In order to prevent the spread of parasites, proper quarantine protocols should be established for any and all new additions, be they fish, plant or invertebrate.

Diagnostic Processes

In order to determine the primary cause of your fish’s gasping, you need to check your water chemistry ASAP with a liquid-based test kit opened within the last year. If the water test results are all within normal range, you will need to setup an appointment with your aquatic veterinarian. They will perform a safe physical exam in order to assess your fish’s gill condition and look for any underlying disease. Often, a gill biopsy sample will be taken in order to look at it under the microscope. Sometimes, additional samples may need to be sent off to a lab for more testing, such as for viral testing.


Once you have tested your water chemistry, you should take immediate steps to correct any abnormalities. Issues with your nitrogen cycle, elevated ammonia, nitrite or nitrate, can be corrected quickly with a 50% water change. Check your tap water for chlorine or ammonia (chloramine) and treat it with water conditioners before adding it to your aquarium or pond if it does. An inappropriate temperature or pH needs to be corrected slowly in order to prevent fish death from shock. Retest the water daily and continue corrective actions until all of the test results are normal.

Depending on the disease process present, your veterinarian may prescribe antibiotics or additional parasite treatments for your fish. Since there are many causes of gill damage and subsequent gasping, there is no “one size fits all” treatment available. The appropriate medication needs to be used, depending on the type of parasite diagnosed. Resist adding any over-the-counter medications that can weaken your fish and make health issues worse.

How to Prevent Gasping for Air

The best way to prevent a fish gasping for air is proper filter maintenance, regular water testing and strict quarantine protocols for new fish and other additions. Avoid overcrowding the fish, and feed an appropriate amount of a quality diet.

Proper Maintenance

Depending on your aquarium or pond setup, the number of fish, the various species being kept, how much food is being fed, and how often you are feeding, you may need to clean the filtration system fairly frequently or not very often. Fish are far from “maintenance free” pets and will require regular maintenance in order to keep their environment healthy. Just like the air we breathe, the quality of the water a fish swims in is critical to their overall health.

Regular Water Testing

How do you know if your maintenance routine is sufficient? Test your water chemistry. Use a liquid-based test kit, not test strips, to measure ammonia, nitrite, nitrate, pH, kH (alkalinity) and temperature at least once a month for an established system. If you are adding filtration components or more fish, or changing their diet, check daily at first and then weekly until levels are stable. If you are unsure what your parameters should be, ask your aquatic veterinarian for your fish species’ requirements. Replace your test kit once a year for reliable results.

Quarantine Protocols

No one wants to wait to add a new fish or plant to their aquarium or pond. However, those first few weeks after coming home from the pet store is when a new fish is at their weakest and carrying whatever was swimming around the communal pet store or wholesalers’ aquarium systems. Because fish move through the pet stores very quickly, they may not show any signs of illness until after
you bring them home. Once you dump them into your healthy system, there is no going back.

Quarantine involves complete isolation of an individual, so that includes a separate tank, pond or tub with separate filtration. In order to protect your fish, a 4-6 week quarantine period is recommended. How did we come up with that timeline? Well, if you take any fish species, there is a
certain list of bacteria, parasites and viruses that could potentially be a problem. There is an incubation time, where the pathogen resides in the fish, but does not show clinical signs, followed by a clinical presentation, where the fish is actually acting or looks sick. However, not every fish will act the same and some owners will not pick up on signs right away. Your tanks’ temperature will critically affect how quickly all these disease processes occur, and this may not be consistent, especially in outdoor ponds. Warmer water will shorten the processes, but this doesn’t mean you can heat your quarantine tank to make things happen faster. Inappropriate temperatures can severely impact your fish’s immune system and they may “clear” quarantine without issue and still be sick.

Overall, quarantine is extra work, but it could save all the lives of your fish.

Fish gasping at the surface can have many causes. Some are easily fixed, such as poor water quality, but others will take veterinary care to properly diagnose and treat. In order to protect your fish, stick to your regular maintenance regimen, check your water quality regularly and be prepared to quarantine all new additions for a month or up to six weeks in a separate system.