Can Fish Drown in Water?

Can Fish Drown in Water? All Your Questions Answered.

Fishkeeping is not just a hobby, but once you’re into that hobby, you’ll discover new facts and incredible realities of underwater life. Most people take this path in hopes of having a pet with fewer dangers and prolonged life. However, with time they realize that it is a hobby that demands constant love and care or can end up in situations you don’t need. One of the questions we at AboutFishTank have received was about can fish drown in water? 

The simple answer to ‘can you drown a fish in a fish tank, or how can fish drown in water’ questions is no, but they can definitely suffocate in water and eventually die. But this answer does not justify the series of questions that come after, like what causes this, why fish suffocate in water when they are made to live underwater, how can we prevent this. So to answer all your questions, our experts have decided to write a comprehensive, detailed guide. So let’s start with 

How can a fish suffocate in water? 

Fish can live underwater, but they need oxygen to do so. Fish have adaptive gills, working as their respiratory system as they don’t have lungs, to help them extract dissolved oxygen in the water for normal breathing.

can fish drown in water and how do they breathe?

There is not one reason that your fish is suffocating underwater. We have compiled a list of important elements that can help you identify what is causing this suffocation. 

  • Low Oxygen Level
  • Water Conditions 
  • Parasites and Gill diseases 
  • Body Modifications and Breeding

Low oxygen level

Fish need certain oxygen levels in their surroundings, whether in the ocean or in the aquarium, without which they can quickly suffocate. Most people refer to this suffocation as the drowning of fish.  

So to maintain the correct oxygen level in the aquarium, you must know what does dissolved oxygen means. Dissolved oxygen is the scientifically determined measurement to determine how much oxygen is in a certain amount of water. The levels of dissolved oxygen are usually influenced by factors like depth of the water, temperature, photosynthesis, outside sources, atmospheric changes, etc. 

Fish are mostly cold-blooded and therefore need less oxygen because of slow metabolism. Opah is the only warm-blooded fish species that circulates warm blood. The rate of suffocation is relatively higher for fishes kept in aquarium or fish tank because the fish tank is more prone to cause a low level of oxygen for fish. 

Causes of low oxygen level 

One of the elements influencing this lower level of oxygen in the wrong tank size chosen for the fish as the small amount of water will quickly run out of oxygen. However, there are few other elements important to learn about. 

  • Overcrowding of fish can cause a decreased level of oxygen in the tank because too many fish in a compact area will need constant addition of oxygen.
  • Live plants in the dark aquarium may cause them to release CO2
  • Lower Light levels
  • A higher temperature than recommended
  • Excess waste and irregular water cleaning
  • Algae Blooms
  • Decomposing plants 
  • Salinity levels 
  • No or slow water movements
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What are the Signs of Low Oxygen in Water? 

You can easily examine and monitor your fish to identify whether there is low oxygen in the tank or not. A few of the tell-tale signs of low oxygen level are if your fish is:

  • Have labored breathing or rapid gill movements
  • Lethargic 
  • Spending more than usual time near the water surface
  • Not eating at all or eating less

These signs need immediate attention and therefore you must change a minimum of 50% of the water to bring more oxygen to the tank. Once done, you can use one of the following methods to keep the oxygen circulation running to ensure a healthy environment for your fish. 

How to prevent low oxygen levels in Fishtank?

How to prevent low oxygen levels in Fish Tank?

  1. Live Plants

    You can use some more plants in your fish tank as they are one of the sources that maintain oxygen levels through photosynthesizing. However, this should be done carefully as more live plants mean too much oxygen, and fish need a balance of oxygen and hydrogen level to survive.  Moreover, some fish may rely on ram ventilation and need to swim forward to push water to gills to breathe; if caught in one of these plants, they stop swimming, causing them to suffocate. On the other hand, few species of underwater plants, in some circumstances, will release carbon dioxide CO2, eventually causing suffocation. Therefore, good maintenance, monitoring, and trimming will help you prevent a lack of oxygen. Moreover, some plants may need fertilizers with CO2 injections, causing hurdles for you to maintain the correct oxygen level. 

  2. Air Pumps

    Air pumps are an alternative tool that you can use in aquariums to keep the oxygen circulation running by bringing oxygen-depleted water up to the surface. You can also use wavemakers, bubble makers, and powerheads to create aerating movements in the water. However, make sure that you keep the recommended water movement to keep the flow steady for the fish type you have in the fish tank. 

  3. Do not overcrowd the fish tank

    It is essential to follow the fish care guides we have on our blog to know more about the requirements of each fish. You must follow the tank size and numbers of fish allowed in a specific size. Too many fish can also decrease the levels of oxygen in the fish tank. 

  4. Increase surface Area

    It is suggested to use long fish tanks than tall fish tanks. Moreover, regularly check for salinity, pH, and other water parameters to keep the oxygen level ideal for the types of inhabitants.

  5. Check Temperature

    It is vital to maintain the right temperature as fish tanks with high temperatures will have low oxygen. This can be a complex issue if your fish tank is full of tropical fish. To maintain the temperature correctly, some aquarists suggest using a fan and air chiller when the temperature is higher than needed.

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Water Conditions

An uncycled tank can be dangerous for a new fish, moreover, the water conditions play a vital role in keeping a healthy fish. Overcrowding decreases the oxygen level but can also spike ammonia levels in the water column. If fish are exposed to this ammonia they can be the victim of ammonia poisoning, burns as if they are bleeding, lack of appetite, low energy levels, and lack of ability to breathe properly. If left for too long, these water conditions can cause suffocation to your fish. Therefore it is important to know why maintaining the pH level is important and how you can raise or lower the pH levels.

Why pH is important to not drown the fish

Ammonia is not the only element that endangers the fish in the aquarium; the second element that can easily kill your fish is nitrate in the water cycle. Nitrate enters the bloodstream of the fish once the and binds the hemoglobin. It makes fish unable to receive oxygen resulting in painful suffocation and death. To prevent this it is important to reduce nitrate levels

You can also take points from our complete guide on new tank syndrome and the ideal water cycle. 

Parasites and Gill Diseases 

As mentioned above, fish need gills to extract dissolved oxygen; however, these gills are very sensitive to parasites and gill diseases caused by these parasites. 

Most parasites include flatworms and fall under the class of Monogenenea. Such parasites and commonly found on the skin or in the fish gills. Dactylogyrus genus is another slimy parasite (gill fluke); it usually attaches itself to Goldfish, Koi fish, and carp (Cyprinidae family). 

These flukes need a host to survive for several hours after initial free swimming. This parasite can cause irritation and inflamed gills that make fish instinctively scratching their gills to hard surfaces resulting in gasping for air, lack of appetite and energy. If not succumbed to these parasites, these fish can fall victim to other infections from inflammation and scratching. Ich is also a common cause of gill disease and can have long-lasting effects on fish survival. It can be a complex disease, so we have separately explained it in our complete guide on ich (Ichthophthirius multifiliis).

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Bacterial gill disease (BGD) and Amoebic gill disease (AGD) can also cause suffocation to fish. Bacterias like Flavobacterium branchiophilum and F. succinicans can cause your fish to become sluggish and less responsive to outside stimuli. Other symptoms may include loss of appetite and fish stationing themselves directly in the new water flow. It is to indicate a lack of oxygen passing across gills because of bacteria. If not tended on time, the over multiplication of bacterias can cause lack of oxygen inhalation through gills, eventually causing suffocation or drowning in layman’s terms. 

Body Modifications Because of Control Breeding

Unfortunately, the beauty in the aquarium trade comes with its price. As some of the most beautiful fish in the market are the results of controlled and selective breeding to come up with desirable body modifications. Betta fish is the prime example of this; the body modifications of labyrinth organ and long tails were intended to help them breathe by gulping atmospheric air to swim up to the surface. However, because of over breeding, these tails are the reasons for them not being able to swim upwards because these tails drag them down. It is important to have an adequate water movement source in the fish tank and to follow the complete care guide for Betta fish. 

Can fish drown in water if they are pulled Backwards?

Yes, they can; the reason for suffocation is not able to absorb the needed dissolved oxygen. When you pull a fish backward, the water flows in the opposite direction making it difficult for their gill to access the oxygen. However, some might still be able to breathe; however, pulling them backward can make them exhausted and lethargic, eventually suffocating them.

How long does it take for a fish to drown?

Three to four minutes of no gill movement are enough to suffocate a fish so it is important to know the symptoms of suffocation like rapid gill movement and gasping to increase the oxygen level immediately.


So can you suffocate a fish in the water? Yes, absolutely, and it is what most new fishkeepers experience. To prevent this ‘drowning,’ you must know the symptoms and causes of low oxygen levels. Maintain the water conditions and follow the guides on how to care for your fish. We hope that this guide has answered all your queries; if not, submit your question below in the comment section. 

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