Can Your Fish Drown in Water?

Wait. What?

If fish live underwater, how could fish drown? 

It’s a straightforward no, they can’t drown, however many things could happen that could cause a fish to not be capable of breathing properly until the fish can suffocate and then ‘drown.

The reasons behind this could be due to low levels of oxygen within the waters, unsteady factors in water like parasites and illnesses, or insufficient selective breeding.

Read on to learn all you should learn about how oxygen gets present in water, the way fish breath, as well as what might cause a fish to drown.

Dissolved oxygen

In order to comprehend the ways in which the levels of oxygen in water impact fish, it is necessary to understand how oxygen is transported from air to the water first. 

Dissolved oxygen (DO) is the scientific term that determines how much oxygen is present in the water and is ready to be utilized in living creatures. 

Dissolved oxygen is affected by many factors such as depth temperature, temperature, atmospheric exchange, external sources as well as photosynthesis.

Temperature and depth

Cold water holds more dissolved oxygen while warmer water holds less dissolved oxygen. 

That means when the surface temperatures of water are at a low level (as there is no exchange interference with the atmosphere and water because of the ice) the concentration of dissolved oxygen will be very high.

However, when the temperatures of the surface are high, the dissolved oxygen levels will be lower.

Seasons, in addition to altitudes and latitudes greatly impact the amount of dissolved oxygen is actually present within the column of water. 

Salinity can also affect the concentration of freshwater compared to saltwater systems. This is among the main reasons there is concern that the temperature average of Earth increasing.

As the climate warms, the surface waters are also warming and decreasing the circulation of oxygen. The organisms that require oxygen to survive could be facing decreasing levels of oxygen dissolved.

Exchange of atmospheric energy

How does oxygen get into the water column first? One of the most common ways that oxygen can enter the water column is via surface exchange. 

In the majority of cases, this happens through the mixing of atmospheric oxygen with water by way of waves and wind. 

This implies that rivers that are turbulent tend to contain higher levels of oxygen dissolved than lakes that are stagnant.

Other sources

They eventually feed to larger water bodies, however, taking the dissolved oxygen in them and influencing the natural concentrations in these regions. 

Certain streams are also get being fed by groundwater that can influence the concentrations of dissolved oxygen.


In addition, just like trees go through photosynthetic processes, aqua plants, as well as vegetation, can also convert the carbon dioxide they absorb into oxygen when they digest the food they consume. 

Particular autotrophic plankton is known as phytoplankton play a significant role in the process of regulating the levels of oxygen in the dissolved state by doing photosynthesis in the daylight in the surface waters.


But, the organisms which do not undergo photosynthesis go through respiration instead which converts oxygen to carbon dioxide. 

This is the case for snails, fish and crabs and also the phytoplankton we discussed in the past!

One of the most significant kinds of organisms that make use of respiration is bacteria. When nutrients and minerals enter the system algae and other species of photosynthetic life start to flourish in these environments that are eutrophic.

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This is typically due to the evaporation of fertilizers as well as other solutions rich in nutrients that are unnaturally entering the ecosystem. 

The algae may grow so dense that the water becomes stained green, and prevents the light source beyond the initial several inches. The result is that the aquatic plants to become starved because they are unable to process photosynthesis.

Then the algae begin to die because the extra nutrients are absorbed and eliminated out of water. This is when the bacteria begin to break down the decaying algae as well as other plants. 

Because there’s a lot of this food source to ensure the thriving population of bacteria the numbers grow and respiration is also increasing, reducing oxygen levels while they breathe. As oxygen levels rapidly decline, the water will become anoxic.

If there is an absence of oxygen, the organisms that require oxygen for survival typically cease to exist. These areas are known as dead zones because aquatic life is not able to sustain itself.

How do fish breathe?

Fish have gills that permit aquatic animal to breathe. They are a large capillary network that is filled with blood, providing large areas of surface to exchange carbon dioxide and oxygen. 

It is worth noting that there are invertebrates and fish that breathe both within and outside of it However, we won’t be discussing the physiology and physiology of these kinds of animals in the present article. For common fish:

Fish first absorb oxygen via their mouths. Then, they create pressure in their mouths, which causes water to flow through the gills’ thin layer. 

The oxygen in the dissolved form circulates into the bloodstream due to oxygen levels being lower in blood than the water surrounding it. Carbon dioxide is also released through the gills and back in the ocean.

What happens if the fishing line is pulled forwards, and isn’t able to take in water through its mouth, as it would if you’re fishing with a line?

Can sharks swim backwards?

It is likely that you have heard that sharks require to swim continuously to breathe. Although some species do not fall under this rule, and are able to breathe the same way as other fish species, generally it’s true that sharks are likely to drown in the absence of a fresh inflow of water through their gills. What if a shark could reverse its swimming?

Sharks are the sole type of fish that is unable to swim backwards, because of the shape of the pectoral fins, which can’t change curvature. But, if they could reverse their swimming, or to be pulled back by a fisherman, they would likely to be suffocated.

Gills are designed to expell and process water but not to receive water. The reverse motion could result in water being forced into the gills. This would interfere with the respiratory system’s normal function and eventually resulting in the fish being unable to breathe. This could lead to drowning.’

The most simple question is: will fish drown?

Fish can be ‘drowned’ for the lack of a better term. However, it’s more appropriate to consider it an instance of suffocation in which oxygen levels are low and the fish aren’t able effectively remove oxygen out of the water due to reasons of one or the other. In the following sections we’ll look into the causes that fish could drown.

The long and complicated answer

If you’re searching for details about the reason your fish in the aquarium may be drowning and died, we must investigate the reasons that could cause an absence or lack of oxygen within the column. We’ll be looking on algae blooms as well as water conditions, diseases , parasites as well as body modifications.

Algae blooms, Eutrophication

As we have discussed previously that an over-supply of nutrients can lead to algae blooms, which then increase the amount of bacteria present, which depletes the oxygen concentrations in water. If there isn’t sufficient oxygen levels in the waters to allow fish to breathe, they will eventually die.

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The most dangerous algae blooms (HAB) typically are made up of bacteria known as cyanobacteria or blue-green algae which could cause harm to humans. be aware that there are many algae blooms that are dangerous in the sense that they cause hazardous conditions. But, the water around them can easily be contaminated , and can cause illnesses if consumed or splashed in.

In these zones, shellfish may also filter the water by absorbing any toxic substances that may be present. Consuming shellfish can cause paralytic shellfish poisoning (PSP) and those suffering from symptoms of this condition should seek medical assistance immediately.

A single of the more well-known dead zones is found at the river’s mouth. Mississippi River. It is the result of fertilisers from farms along the river getting removed until they are concentrated at the beginning of the Gulf of Mexico. A lot of shrimp farms, fisheries or oyster farm have been affected because of this water, which does not have enough oxygen for health conditions.

Conditions of water

Why is it that you can’t add fish to a recently cycled tank? If you’re unsure of what the solution to that question is, then we suggest that you go through our guide to cycled fish tanks here.

You may be aware that you shouldn’t however, you may not know the precise reasons for why a tank that isn’t cycled can be harmful to new fish. One of the biggest issues is that any new tank is going through an entire water cycle that begins with ammonia. Keep in mind that ammonia may also increase when the tank is overstocked. If there is ammonia within the column of water any fish could be exposed to poisoning caused by ammonia.

Ammonia may cause burns to occur on the fish. This makes the gills appear as if they’re bleeding. The spotting can extend to the rest of the body. 

Then it is possible that the fish can be gazing for air near the surface and not eating and lying at in the middle of the tank. If it is left in these temperatures for too long the fish may not be able to breathe the oxygen it requires, which can lead to the fish dying.

Following ammonia, nitrite enters the process, and it is a danger factor that can swiftly endanger your fish. Once your fish is exposed, nitrite gets into the bloodstream, and it binds to hemoglobin, where oxygen is supposed to be been attached, causing the fish to suffocate and then drown.

Diseases and parasites

Fish require gills in order to breathe oxygen dissolved into their blood, but what happens if Gills have been damaged due to parasites or diseases? 

It is true that the gills are an extremely frequent site for both external and internal parasites to develop on fish. Most of the parasites that are found fall into the Monogenenea class and include flatworms which are typically found in the skin, or within the gills.

One parasite that’s slimy is gill fluke (Dactylogyrus Genus) which is a common occurrence with members belonging to the Cyprinidae family, such as goldfish, koi, as well as carp. They are at first free-swimming and must find an animal host after a period of time to live. 

It is common for them to have inflammation of the gills, and may cause irritation and make it scratch the gills over hard surfaces. Fish may also struggle to breathe properly as well as become irritable and lose appetite.

Unfortunately, many fish fall victim to parasites because they are extremely infectious and can multiply quickly. Many fish are further affected by fungal or other bacterial illnesses caused by scratching and inflammation or aren’t able to extract enough oxygen out of the water, leading the fish to drown.

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More often, aquarium fish usually have an illness called ich ( Ichthyophthirius multifiliis), which can be found in the gills and can cause lasting effects in the event that the fish is able to survive.

Fish can even drown because of different factors like fungal or bacterial infections. One of the issues that Salmonid fishing fleets encounter is bacteria gill diseases ( BGD); interestingly it is believed that BGD is only a problem in the commercial sector and hasn’t affected the wild population of fish.

The most notable thing is that the bacteria Flavobacterium branchiophilum as well as F. succinicans, can cause fish to be irritable, suffer an appetite loss, and are less responsive to stimuli from outside. 

Fish that are exposed also tend to sit directly in the flow of fresh water, signalling that they require more oxygen. If they are not treated, fish could die if bacteria multiply and there is not enough oxygen is circulating through the gills.

A similar bacterial disease is called amoebic Gill Disease (AGD) that can result in death of fish.

Modifications to the body

The most stunning aquarium fish are selectively bred to display the most desirable body changes which can cause animals to die. A great and tragic example for this would be the Betta fish.

Betta fish are an exceptional species to take into consideration in relation to breathing. They have an extra organ known as Labyrinth Organ which permits them to reach an elevated surface in the ocean and breathe in atmospheric air. 

This organ is believed be the result of an urgent need for oxygen in water that has low levels of oxygen. Betta fish are also able to pull oxygen from the water through the gills, similar to other fish.

Betta fish with tails that are long are also able to reach the surface to breath in air and draw in the water with their gills. But, they have been so heavily breed so that the tails pull to the bottom, making them hard to come up for oxygen or swim. 

Due to this, the fish are exhausted and typically end up leaning to the edge of a decorator or in an aquarium’s bottom.

If there is a lack of movement of water within the aquarium, oxygen levels will be rapidly depleted, with the fishing fish struggling to breath and not able to take in more oxygen. 

After the fish has taken all the oxygen it can out of the water column through its gills, and cannot reach the surface to breathe it will drown.

If you’re thinking of buying a betta, ensure that you research the most information you can in order to avoid this from occurring. 

If you have already a fish that has an extended tail, you need to ensure there’s sufficient water circulation (without making it harder for your fish) and ensure that the water is healthy and oxygenated. 

If you’d like more information about how excessive finnage can cause drowning look up our Rosetail betta – the downside of beauty blog here.


Can fish drown? Absolutely. A fish that drowns is certainly not a pleasant experience.

Maintain the levels of dissolved oxygen in your aquarium by ensuring plenty of water movement as well as exchange with air on the surface. 

Keep your water’s parameters in check and look for signs of diseases and parasites and steer clear of fish with modified bodies. And hopefully you will not have to endure the consequences of drowning when fish die.

If you have additional questions regarding why fish require oxygen, the ways that fish could drown, or the way in which the air and water interact Don’t hesitate to post your comment below!

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