Why Is My Fish Laying On Its Side? Discover the Reasons and Solutions

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If you’re a fish owner, one of the greatest concerns you’d have is if your fish starts swimming or resting on its side. Seeing as that’s not their normal behavior, it could indicate an underlying issue with their health and should be addressed immediately.

There are numerous reasons why your fish might lay on its side including swim bladder disease, injuries, parasites, poor water quality, and even old age. Knowing the reason behind this unusual behavior is crucial to properly address it before it results in death or additional complications.

“You can’t rush something you want to last forever.”

There are several solutions to this problem depending on what caused it. In some cases, you may need to simply change your pet’s diet or adjust the water conditions. Other cases might require more invasive treatments such as medication or surgery, but regardless of how serious the situation seems, there’s always a solution.

In this blog post, we’ll discover the most common root causes of why your fish lays on its side and provide practical tips and solutions for maintaining a healthy environment for your cherished pets.

Water Quality Issues

Have you noticed that your fish is lying on its side or showing signs of lethargy? It could be due to poor water quality in the tank. Here are some water quality issues that may affect your pet fish:

Chemical Contamination

The presence of harmful chemicals in the aquarium can be deadly for the fish. Chemicals such as chlorine, ammonia, and heavy metals can damage gills, fins, and scales leading to death. Additionally, even tap water contains chemicals like fluoride and chlorine which are used to make it potable. These substances might not harm humans, but they can certainly cause problems for aquatic creatures.

“Chlorine gas has long been known to have an acute toxic effect upon fishes, even when present in relatively low concentrations.” – John F. Craig Jr., Department of Fisheries and Allied Aquacultures at Auburn University

To prevent chemical contamination, use a good water conditioner to remove any pollutants from the water before adding it to the tank. Do regular partial water changes to keep the water clean and toxin-free.

Algae Blooms

Algae blooms can occur when excess nutrients such as nitrates and phosphates accumulate in the water. The overgrowth of algae will reduce oxygen levels in the aquarium, making it harder for fish to breathe. Algae blooms can also release toxins into the water, posing a significant threat to the aquatic life.

“Algal blooms reduce water quality by reducing light penetration, causing dissolved oxygen depletion during periods of darkness….” – EPA

You can prevent algae growth by regularly cleaning the aquarium, keeping lights on only for 8-10 hours per day, reducing feeding frequency, and avoiding overfeeding. Ensure that the filtration system is working correctly and replace filter media when necessary.

Temperature Fluctuations

Fish are sensitive to temperature fluctuations, and rapid changes in water temperatures can cause stress, disease, or even death. Temperature shocks occur when the fish tank heats up quickly due to exposure to direct sunlight or poor heater control. Fish exposed to high temperatures will try to escape by jumping out of the water, making it a severe concern for pet owners.

“Rapid changes in pH, salinity, and other environmental factors like temperature or light intensity can negatively impact growth, behavior, and reproduction.” -Patrick Cooney, Director of Education and Citizen Science at Living Resources Corporation

To avoid sudden temperature fluctuations in the aquarium, place your fish tank in an area that doesn’t receive direct sunlight, use appropriate heaters and thermometers, and monitor the water regularly. You can also keep a backup power source and have a plan in case of a power outage.


Aquatic creatures, including fish, are vulnerable to ocean acidification resulting from excessive CO2 concentrations in the atmosphere. The result is lower pH levels in the water which makes it more acidic. Consequently, this threatens calcium carbonate structures such as the shells and skeletons of fish, clams, oysters, and corals plus disrupts their ability to reproduce.

“When seawater becomes too acidic, it corrodes the animals’ protective shells and prevents them from forming new ones…” – EPA

To minimize the impacts of acidification on fish, persons should take carbon emission reduction measures like using eco-friendly energy sources in households, factories, transport sector, wildlife habitats, etc. Also, you may want to invest in marine life monitoring applications or software that can detect pH levels in the water so that you become aware of any change.

Ensuring the best possible water quality is very important for a healthy aquarium. The above water quality issues must not be taken lightly, and you should work to ensure the optimal living conditions for your fish pets. Remember that prevention is always better than cure, so make efforts right now to avoid encountering these issues in your tank.

Lack of Oxygen

One possible reason for your fish laying on its side may be due to a lack of oxygen in the water. Fish need oxygen-rich water to survive, just like we need air to breathe.

If the water in your aquarium is stagnant or not well-oxygenated, it can lead to a condition known as hypoxia. Hypoxia occurs when there’s not enough dissolved oxygen in the water to keep your fish healthy, which can cause them to become stressed and lethargic.

In addition to causing your fish to lay on their sides, hypoxia can also lead to other health problems, such as gill damage, increased susceptibility to diseases, and even death.

“Poor water quality is the number one killer of aquarium fish.” -Kevin Fitzsimmons


Another potential cause of your fish lying on their side could be due to eutrophication. Eutrophication occurs when excess nutrients, such as nitrogen and phosphorus, enter into a body of water, causing an overgrowth of algae.

This buildup of organic matter can decrease the oxygen levels in the water and create toxic conditions for fish. If left unaddressed, eutrophication can lead to sudden fish kills and other environmental problems, including foul odors and unsightly blooms of green or brown-colored scum floating on the surface.

To prevent eutrophication from occurring, it’s important to maintain proper nutrient balances in your tank by regularly changing out old water with fresh, clean water, reducing feeding amounts, and removing any excess debris or dead plant matter that might be contributing to the buildup of nutrients in the water.

“Eutrophication is a major threat to aquatic ecosystems and human societies alike.” -UN Environment Programme

Thermal Stratification

The final reason why your fish might be lying on their side could be related to a phenomenon known as thermal stratification. During the summer months, some aquariums may experience temperature stratification, where warm water remains at the top of the tank, while cool water sinks to the bottom.

This can create pockets of low-oxygenated water near the bottom of the tank, making it difficult for your fish to breathe. If you notice that your fish are spending more time at the surface of the tank than usual, or if they’re struggling to swim down to the bottom, this could be a sign of thermal stratification.

To prevent thermal stratification from occurring, make sure to use an aquarium thermometer to track the temperature of your tank regularly and adjust accordingly. You can also install a water circulator or air pump to promote better water circulation and oxygenation throughout the entire tank.

“Temperature is key to aquatic life and essential for its proper functioning.” -European Commission Joint Research Centre

If you suspect any of these causes could be behind your fish laying on its side, it’s important to act quickly to restore your tank’s health. This includes performing regular water changes, increasing filtration rates, and implementing nutrient control strategies. By taking steps to improve your fish’s environment, you can help them stay healthy and happy in their underwater home.


Excessive Nutrient Input

One of the primary reasons why your fish may be laying on its side is overfeeding. Feeding fishes once or twice a day is enough to sustain their nutritional needs. However, sometimes aquarium owners tend to feed their fishes more frequently without knowing the repercussions that come with this behavior.

Feeding too much food can lead to a build-up of nutrients in the water, which leads to excessive nutrient input. Fishes often swim in an environment where there is limited space for movement. Overfeeding, coupled with a confined living space, can create hazardous conditions leading to sickness and death among the species inside the tank.

Waste Accumulation

In addition to causing excess nutrients due to overfeeding, another cause could be waste accumulation in the aquarium. When you overfeed your fishes, the extra food goes uneaten, thus sinking to the bottom of the tank. Bacteria act on these remains producing waste materials which accumulate over time.

The accumulation of such debris poses serious risks to the health of the fishes as the material lowers the oxygen levels and increases ammonia content. Ammonia at high concentrations is toxic to aquatic organisms, making it very dangerous even in small quantities.

“Fish are highly sensitive animals. They have evolved to live in environments of perfect chemical balance so any alteration in that balance is going to affect them in some way.”
Rebecca McKeown, animal behaviour expert.

Bacterial Growth

In an aquarium, many different types of bacteria coexist with the fishes. Some of these bacteria are beneficial because they help break down waste products through a process called biofiltration. Unlike good bacteria, harmful bacteria can easily develop if not checked, and the most common cause of bacterial growth is overfeeding.

Excess food particles, waste products and uneaten debris provide conducive conditions for bacterial growth. Once these bacteria grow out of control, they can attack the fishes in several ways such as infecting them with diseases, leading to organ failures or even death.


The accumulation of waste products, uneaten food debris, and other materials lead to toxicity levels becoming increasingly high inside an aquarium. The concentration of toxins can build-up so much that fish become lethargic before finally lying on their side when too weak.

Note: It is essential to monitor and manage your water quality regularly by testing nitrate, ammonia and PH levels. Always carry out regular water changes, use filters correctly, remove any dead plants/fishes immediately to avoid accumulation of dangerous chemicals that may harm fish life.

  • Avoid overfeeding, which can cause hazardous aquatic conditions, including excess nutrient input, waste accumulation, bacterial growth, and toxicity.
  • No single solution works against all problems; there are different types of medications available based on symptoms shown by infected fishes, thus consulting a veterinarian aquarist is necessary.
  • Fish disorders can be easily prevented if good hygiene practices are observed where owners take the needed measures to maintain healthy living environments for their pets.

Swim Bladder Disease

If your fish is laying on its side, swim bladder disease could be the culprit. Fish have a swim bladder that they use to control their buoyancy and move around in the water. When this organ becomes infected or damaged, it can lead to swimming issues, including rolling over and floating to one side.

Bacterial Infection

Bacterial infections are a common cause of swim bladder disease in fish. These types of infections often occur when a fish’s immune system is compromised due to poor water conditions or stress. Symptoms of bacterial swim bladder disease may include difficulty swimming, loss of balance, and lethargy.

“Bacterial infections are more likely to occur in dirty tanks or aquariums with stagnant water,” says Dr. Joanne Paul-Murphy, professor of exotic animal medicine at Veterinary Medical Teaching Hospital at the University of California, Davis.

To prevent bacterial infection, keep your aquarium clean and maintain steady water parameters. Make sure you do not overcrowd your tank, as too many fish in one tank can increase the risk of disease transmission.

Dietary Issues

Poor diet can also lead to swim bladder disease in fish. Feeding your fish low-quality food or overfeeding them can result in digestive issues that affect the swim bladder. This can lead to your fish becoming immobilized and laying on its side.

“Fish may lay on their sides if they are constipated or bloated from eating too much,” says Dr. Scott C. Linden, an aquatic veterinarian at Keystone Hatcheries in Pennsylvania.

To avoid dietary-related swim bladder disease, make sure you provide your fish with high-quality food in appropriate portions. Avoid feeding them dry pellets exclusively, as these can expand in their stomachs and cause blockages. Consider supplementing their diet with live or frozen foods, such as brine shrimp or bloodworms.

If you suspect your fish is suffering from swim bladder disease, it’s important to take action quickly. Consult a veterinarian who specializes in aquatic animals for diagnosis and treatment options. With proper care and attention, your fish can recover from this condition and regain its mobility and balance.

Parasites and Diseases

If you’re noticing your fish laying on its side, then it’s likely that they are suffering from some type of parasitic infection or disease. It’s important to know the symptoms and treatment options for these common ailments in order to save your fish.

Ichthyophthirius multifiliis

Ichthyophthirius multifiliis, also known as “ich,” is a highly contagious parasite that can quickly infect an entire tank of fish. If your fish are showing signs of white spots on their fins or body, rapidly breathing, and laying on their side at the bottom of the tank, then they may have ich.

To treat ich, there are many over-the-counter medications available at pet stores that can help rid your fish of this pesky parasite. However, it’s important to follow the dosage instructions carefully to avoid harming your fish. You can also try reducing the temperature of your water and adding salt to create an inhospitable environment for ich.

“Ich is one of the most common diseases found in aquariums due to poor hygiene practices.” -Fishkeeping World News

Columnaris Disease

Another potential cause of fish laying on their sides is columnaris disease, which is caused by bacteria in the water. Symptoms of columnaris include frayed or ragged fins, ulcers on the skin, and a loss of appetite.

To treat columnaris, antibiotics will be required. It’s important to not only treat the infected fish but also complete a thorough cleaning of the tank and any accessories within it to prevent further spread of the disease. Additionally, stress reduction measures such as frequent water changes and good filtration should be put in place to keep your fish healthy.

“Columnaris is often mistaken for fungal infections due to their similar appearances, but it’s important to properly diagnose the disease before treating it.” -International Betta Congress

Gill Flukes

If your fish are gasping for air, rubbing themselves against objects in the tank, and laying on their side, then they may have gill flukes. These parasites attach themselves to the gills of the fish and can cause severe damage if left untreated.

To treat gill flukes, medicated food or baths can be used to kill off the parasite. Additionally, ensuring clean water and proper filtration will also help prevent future outbreaks. Keep an eye on your other fish as well, since gill flukes can easily spread between a community of fish.

“Gill flukes are harder to spot than other types of parasites, so it’s important to keep a close eye on the behavior of your fish.” -Aquarium Source

If your fish continue to lay on their side even after treatment, it’s important to consult with a veterinarian who specializes in aquatic animals. Quick action and proper care can make all the difference when it comes to saving the lives of your fish.

Stress and Trauma

If you found your fish laying on its side, the first thing to consider is stress or trauma. Fish can quickly get stressed by different factors such as insufficient water quality, incompatible tankmates, sudden changes in temperature and light, among others.

You should pay attention to any signs of discomfort that your fish might be displaying because it will help prevent future occurrences of this kind. For instance, if the behavior occurs after relocating them to a new tank setup, then they are likely expressing their frustration with living conditions.

In case of severe impact injuries or illnesses caused by parasites, fungi, or bacterial infections, make sure that you seek veterinary attention. Your veterinarian may prescribe some medication to ease their pain, reduce swelling, and heal wounds.

  • Check for any noticeable physical injury or damage.
  • Purchase a quarantine tank to separate the unhealthy fish from other healthy specimens.
  • Regularly change their water supply and maintain adequate temperature levels monitoring pH levels daily.


The transportation of fish between aquariums can also cause temporary adverse effects, especially when moving relatively long distances. Such trips require special considerations regarding how to transfer the fish without causing much harm or exposing them too much shock.

In an attempt to facilitate safe travel, wrap the plastic bag containing the specimen by wrapping moist towels around it to regulate water evaporation rates while keeping it insulated.

“During the transport period, stressful situations may occur due to environmental gas concentrations and low oxygen pressure. Anesthetic substances used for sedation during transport have been shown to produce significant physiological stress.” -International Journal of Animal Science

Also, remember to measure the water temperature against cold temperatures to identify any cold-shock risks resulting from temperature changes. Consider investing in fish bags with oxygen supply to provide fresh air during transport and protect them against lack of it due to extended travel periods.

Aggressive Tank Mates

In a communal aquarium, adult aquarium fish may get into a fight or chase after one another. It’s essential to select the correct tankmates for your fish and ensure harmonious cohabitation. Aggressive fish species such as Bettas, Gouramis, and Cichlids that typically live alone won’t take kindly to having other tank mates encroach upon their territory.

  • You can introduce new fish members gradually over an extended period depending on your existing fish’s temperament.
  • Observe general behavior to see if there are any issues such as excessive aggression between groups fighting for resources.
  • A separate feeding space will reduce territorial behavior while providing proper care by cleaning water filtration units.

If introducing too many fishes at once, you can disrupt the delicate balance that exists in the aquarium environment leading to stress on fish culminating in fatalities caused by injuries, exhaustion, or starvation.

“Combining different types of aquarium fish has been viewed as appealing given its cost-effectiveness and diversity benefits; however, strict observations should be done before introduction to avoid attacks.” -Hindawi Journal of Environmental Sciences

The laying of the side isn’t necessarily out-of-the-ordinary behavior among fish species in itself. You look out for physical symptoms of injury, notice how much stress they’re under, and sound like using monitoring techniques highlighting anything amiss. Albeit keeping track may seem challenging initially, managing your pet’s health becomes easier when conducted regularly, enhancing longevity and enjoyment of these fascinating creatures’ company.

Frequently Asked Questions

Why is my fish laying on its side?

There are several reasons why your fish may be laying on its side, including swim bladder disease, injury, infection, or poor water conditions. It is important to identify the underlying cause to properly treat your fish.

What are the possible reasons for a fish to lie on its side?

A fish may lie on its side due to swim bladder disease, injury, stress, infection, or poor water quality. It is important to observe your fish’s behavior and assess the water conditions to determine the cause.

Can a fish lying on its side still be alive?

Yes, a fish laying on its side may still be alive but it is a sign of distress. It is important to identify the underlying cause and provide appropriate treatment to improve the fish’s condition.

How can I determine if my fish is sick or just resting?

Observe your fish’s behavior and look out for any abnormal signs such as lethargy, loss of appetite, abnormal swimming patterns, or discoloration. If you suspect your fish is sick, consult a veterinarian or aquatic specialist.

Is there anything I can do to help my fish recover?

Yes, depending on the underlying cause, there are several steps you can take to help your fish recover. This may include water changes, medication, or adjusting the fish’s diet and environment. Consult a veterinarian or aquatic specialist for appropriate treatment.

What preventative measures can I take to avoid my fish lying on its side?

To prevent your fish from lying on its side, maintain a clean and healthy environment, avoid overfeeding, provide adequate space and hiding spots, and monitor water conditions regularly. It is also important to quarantine new fish before introducing them to an established tank to prevent the spread of disease.

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