The Shocking Truth: Do Fish Suffer from Seizures Too?

can fish have seizures

A seizure is a sudden, uncontrolled electrical disturbance in the brain. It can cause changes in behavior, movements, feelings, and levels of consciousness. 

There are many different types of seizures. Some involve the entire brain (generalized seizures), while others only involve part of the brain (focal seizures).

The most common types of generalized seizures include:

  • Absence seizures – These cause a short loss of awareness or staring spells. They usually last less than 30 seconds.
  • Tonic-clonic seizures – Also known as grand mal seizures, these cause stiffening of the limbs (tonic phase) followed by jerking muscle movements (clonic phase). They may cause loss of consciousness.
  • Myoclonic seizures – These brief shock-like jerks of a muscle or group of muscles.  
  • Atonic seizures involve a loss of muscle control that may cause sudden collapse or nodding of the head.
  • Clonic seizures consist of repeated or rhythmic jerking muscle movements on both sides of the body.

Focal seizures affect one area of the brain, and symptoms depend on which part is involved. Common focal seizures include:

  • Simple focal seizures – These do not cause loss of awareness. Symptoms depend on the affected area and may include repetitive movements or unusual sensations.
  • Complex focal seizures – These cause changes in awareness or consciousness. They may result in staring spells, repetitive movements, or unusual sensations. 

In humans, there are many potential causes of seizures, including: 

  • Head trauma or injury
  • Brain infections, such as meningitis or encephalitis
  • Stroke
  • Brain tumor 
  • Genetic conditions that run in families
  • Developmental disorders like autism
  • Degenerative brain diseases like dementia
  • Metabolic disturbances like low blood sugar, low calcium or sodium levels
  • Drugs, alcohol withdrawal, or poisoning
  • High fevers in children
  • Electrolyte imbalances
  • Brain damage related to prematurity in newborns

In some cases, no cause can be identified. These are called idiopathic seizures.

Do Fish Have Brains and Nervous Systems?

Fish have brains and nervous systems that share similarities with mammals, though there are significant differences.

The fish brain consists of several distinct regions, including the telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon, and medulla oblongata.

The telencephalon is considered the fish brain’s most complex part and involves functions like learning and memory. 

Fish brains tend to be smaller and more straightforward than mammalian brains. For example, the telencephalon region is much less developed than the cerebral cortex in mammals.

Fish brains also lack specific structures like the neocortex and corpus callosum in mammalian brains. 

However, fish brains still coordinate essential functions like sensory input, movement, homeostasis, and behavior. Fish have complex behaviors and can learn, socialize, and solve problems.

The fish nervous system consists of a central brain and spinal cord and a peripheral nervous system with nerves running throughout the body.

Fish have sensory neurons to detect stimuli like taste, touch, and vision, and motor neurons control muscle movements like swimming.

In summary, fish have organized and functional brains and nervous systems that allow them to sense, process, and interact with their environments in sophisticated ways—even if their neuroanatomy differs from mammals’.

The presence of brains and nervous systems means fish have the biological structures necessary for seizures to occur potentially.

Can Fish Have Seizures?

Fish are commonly perceived as simple creatures with basic nervous systems. However, emerging scientific evidence indicates that fish can experience seizures like humans and other mammals. 

Seizures occur when the brain has abnormal electrical activity, leading to involuntary muscle contractions and odd behaviors.

All vertebrates, including fish, have brains and complex nervous systems that could allow for seizure activity under certain conditions.

Specific studies have found seizure-like behaviors in several fish species:

  • Zebrafish larvae showed seizure-like convulsions and spasms when exposed to a drug that induces seizures. Their brain activity also resembled that seen during seizures in humans.
  • When exposed to high carbon dioxide levels, rainbow trout displayed unusual corkscrew swimming behaviors, likely indicating seizure activity.
  • Atlantic salmon had seizure-like episodes when undergoing anesthesia before commercial slaughter.
  • Captive tropical fish, such as Oscar fish and Jack Dempsey cichlids, have been observed having seizures, especially in poor water conditions.

Seizures appear most common in captive fish populations, possibly due to environmental stressors, poor water quality, or neurological damage from injuries or illness. However, wild fish may also experience seizures in certain scenarios.

So, a growing body of scientific evidence points to fish having the capacity for seizures under the right triggers. More research is still needed to understand this phenomenon across different species fully.

Causes of Seizures in Fish

Fish seizures can be caused by a variety of factors, including environmental stressors, disease, toxins, brain abnormalities, and oxygen deprivation.

Environmental Factors

Sudden changes in water conditions like temperature, pH, hardness, or salinity can trigger seizures in fish.

Drastic shifts in their environment cause stress, which can lead to neurological dysfunction. Loud noises, bright lights, or high stocking densities may also contribute.


Certain infectious diseases that affect the central nervous system of fish can result in seizure activity.

Some bacterial, viral, fungal, and parasitic infections directly attack brain tissues and neuroreceptors. This neurological damage can make fish prone to seizures.


Exposure to heavy metals, pesticides, and other waterborne toxins has been shown to cause seizures in fish.

Toxic substances interfere with neurotransmission and brain cell function. Fish experiencing toxin-induced seizures may display abnormal swimming behaviors.

Brain Abnormalities

Structural defects in the brain, like lesions, tumors, or physical trauma, can trigger seizures in fish. Improper development of neural networks may also predispose certain fish to seizure disorders. Genetic factors likely play a role as well.

Oxygen Deprivation

Lack of oxygen, a condition known as hypoxia, commonly leads to seizures in fish. When brain tissues don’t receive enough oxygen, neurotransmitter activity becomes impaired. Prolonged oxygen deprivation can cause permanent brain damage and chronic seizures.

Symptoms of Seizures in Fish

Seizures in fish can manifest in several observable symptoms. The most common signs of a seizure in fish include:

Uncontrolled shaking

During a seizure, a fish may exhibit sudden, rapid, and uncontrolled body shakes. This shaking can involve the whole body or isolated areas.

It may appear as violent tremors or convulsions. This is one of the most obvious signs that a fish is experiencing a seizure.

Loss of orientation

Fish suffering from seizures can become disoriented and lose control of directional swimming. They may have trouble maintaining upright buoyancy and equilibrium. A fish having a seizure may swim sideways or upside down involuntarily. 

Floating sideways

Related to loss of orientation, seizing fish often float sideways or belly-up. They are unable to right themselves and regain regular upright swimming.

A fish that suddenly begins floating on its side with no apparent injury could be having a seizure.

Abnormal swimming patterns

Fish experiencing seizures exhibit abnormal and erratic swimming behaviors like darting, looping, or drifting.

Seizure activity can cause a fish to make quick, zig-zag movements, pause, and remain still mid-swim. Their swimming may appear unnatural.

Seizures typically only last a few seconds or minutes in fish. If they are recurring or the fish exhibits any of these symptoms for a prolonged time, it requires urgent veterinary care.

With the observation of a fish’s behavior, seizures can be diagnosed so that appropriate treatment can be administered.

Diagnosing Seizures in Fish

If you suspect your fish has seizures, a veterinarian can help diagnose the condition and determine the underlying cause. Diagnosis typically involves:

Physical Exam

The veterinarian will closely examine the fish and observe any unusual behaviors, movements, or appearance that may indicate seizures. They will look for signs like:

  • Loss of balance 
  • Uncontrolled swimming
  • Stiffening of the body
  • Jerking movements
  • Flared gills

Imaging Tests

Advanced imaging technology can examine a fish’s brain and nervous system. Tests like CT scans, MRIs, or radiographs allow vets to check for issues like:

  • Brain lesions
  • Tumors  
  • Inflammation
  • Abnormal anatomy

Lab Tests

The vet may collect tissue, blood, or fluid samples for analysis. Lab tests can detect underlying problems such as:

  • Electrolyte imbalances
  • Infections
  • Liver or kidney disease
  • Toxins 
  • Metabolic disorders

Analysis of the fish’s living environment may also be recommended to test for problematic water conditions.

Once the underlying cause is found through diagnostic testing, the vet can recommend appropriate treatment options for the fish’s seizures. Proper diagnosis is critical to managing seizures effectively.

Treating Seizures in Fish  

There are several options for treating seizures in fish, depending on the underlying cause. Some treatment approaches include:


  • Anticonvulsant medications like phenobarbital, potassium bromide, or gabapentin may be prescribed to reduce the frequency and severity of seizures. These drugs help stabilize electrical activity in the brain.
  • Sedatives or anesthetics may be used to stop an active seizure. 
  • Antibiotics may be needed if there is an infection causing the seizures.

Dietary Changes

  • Ensuring proper nutrition with a high-quality diet is essential, as metabolic issues can contribute to seizures.  
  • Supplements like vitamin B complex, magnesium, or potassium may help manage seizures in some cases.

Environmental Modifications

  • It is recommended that stressors and stimuli in the tank that could trigger seizures be reduced. This includes maintaining proper water parameters.
  • Providing hiding spaces and regulating light exposure can also help.


  • If a brain tumor, abscess, or other structural abnormality is causing seizures, surgery may be performed. This carries risks but can be life-saving in some scenarios.

The specific treatment plan will depend on the fish’s diagnosis and the suspected cause behind the seizures. Addressing any underlying conditions is critical to managing seizures successfully in the long term.

Preventing Seizures in Fish

Proper fish husbandry and tank maintenance prevent seizures in aquarium fish. This includes maintaining adequate water parameters like temperature, pH, ammonia, nitrites, and nitrates.

Drastic fluctuations in water chemistry can stress fish and make them prone to seizures. 

Regular partial water changes help replenish minerals and dilute waste products. During water changes, a high-quality de-chlorinator is essential to remove chlorine and chloramines from tap water.

Ammonia and nitrites should always test at 0 ppm. Nitrates should be kept under 20 ppm.

Providing a well-balanced diet with variety helps fish stay healthy. Feed high-quality fish food and supplement with vitamins. Avoid overfeeding, which causes waste buildup. Uneaten food should be promptly removed.

Toxins like copper medications, formaldehyde, and cleaning agents can trigger seizures. Limit chemical and medication use.

Quarantine new fish to avoid introducing pathogens—Disinfect aquarium decorations and gravel to prevent disease transmission. 

Responsible breeding practices reduce inbreeding depression and genetic defects that can contribute to seizures.

Know pedigree when acquiring breeder fish—cull offspring with abnormalities. Give fry optimal rearing conditions for healthy development. Maintain genetic diversity within breeding populations.

Fish seizures can often be avoided with proper care, tank maintenance, nutrition, and disease prevention.

However, some underlying health conditions may still lead to seizures despite the best efforts to prevent them. Work closely with a fish veterinarian for guidance.

Caring for Fish with Seizures

If your fish has been diagnosed with seizures, there are some things you can do as an owner to provide the best care and quality of life. 

Monitoring Water Quality

Maintaining excellent water quality is crucial for a fish with seizures. Do frequent partial water changes, test water parameters often, and keep ammonia, nitrites, and nitrates at zero.

Poor water quality can exacerbate neurological issues. Invest in a high-quality filtration system and use supplements like Seachem Prime to detoxify the water.

Feedings and Nutrition  

Provide a nutritious diet with variety. Ensure the fish eats, as seizures can interfere with regular feeding behavior.

Offer food enriched with vitamins and minerals. Soak dry foods in vitamin supplements. Focus on quality over quantity. 

Providing Safety

Take steps to make the tank environment as safe as possible. Remove intricate decor and sharp objects that could injure a fish during a seizure.

Maintain soft substrate. Add plenty of plants and hides for security. Keep tankmates peaceful and levels low to avoid aggression. Dim lighting can also help lower stress.

Monitor the fish closely and be prepared to intervene if a seizure threatens its safety. It is recommended that a hospital tank be ready in case the fish needs separation.

While seizures can’t be prevented, minimizing risks and stress can help reduce occurrences.

Outlook for Fish with Seizures

The outlook for a fish with seizures depends primarily on the underlying cause. With proper veterinary treatment and care, fish that experience occasional isolated seizures can often have a good quality of life.

However, the prognosis is generally worse if the seizures are recurring and difficult to control with medication.

Fish that have an underlying illness or condition causing the seizures may have a guarded prognosis.

In these cases, treatment focuses on managing the seizures and treating the underlying problem if possible. The long-term outlook depends on the fish’s response to treatment.

For fish with idiopathic epilepsy (seizures with no identifiable cause), the seizures may be recurrent and difficult to control.

With patient monitoring, adjustments in medication dosage, and a consistent daily routine, these fish can still have a good quality of life.

However, the owner should be prepared for the possibility of seizures continuing periodically throughout the fish’s life.  

Overall, the prognosis for seizure disorders in fish can vary widely. With prompt veterinary care, proper treatment, and a good home environment, many fish with seizures go on to live fulfilling lives.

While seizures may recur, the outlook can be positive in many cases with dedicated care and management.

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