Why Is My Neon Tetra Swimming Upside Down? (With 5 Quick Solutions)

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I recall feeling extremely worried the first time I noticed my neon tetra swimming upside down. At that moment, I felt like the worst caregiver for my pet. However, over time, I learned how to assist my little fish in recovering. Fortunately, there are several effective ways to address this issue.

Neon tetras typically swim upside down due to a swim bladder disorder, which affects their buoyancy. This disorder can be caused by various factors such as constipation, injuries, poor water conditions, diseases, stress, and swollen organs.

In the following sections, I will guide you step-by-step on how to rectify this condition and prevent it from recurring. I will also highlight some warning signs that indicate your neon tetra may be sick or nearing the end of its life.

Why Is My Neon Tetra Swimming Upside Down?

Neon tetras, like most fish, are naturally oriented to swim right side up. It is not normal for a neon tetra to swim upside down.

An upside-down posture in a neon tetra indicates that its swimming ability has been compromised by internal or external factors. People generally attribute this behavior to three main factors:

1. Swim Bladder Disorder in Neon Tetras

Swim bladder disease is the primary cause of erratic swimming in fish.

The swim bladder is an organ that controls buoyancy in neon tetras, enabling them to maintain their desired depth without exerting much energy.

Whenever the swim bladder’s health is compromised, neon tetras experience buoyancy issues, including sitting at the bottom, swimming vertically, and floating upside down.

The neon tetra does not intentionally swim upside down; it is unable to control it. Swim bladder disease can have several causes, including:

  • Constipation: Excessive food consumption can cause the stomach to swell, exerting pressure on the swim bladder. Constipation can result from poor water conditions, overfeeding, or an inadequate diet. Freeze-dried foods can also be problematic if they expand inside the fish’s digestive tract, causing blockages.
  • Injuries: Neon tetras are known for their aggressive tendencies, particularly among males. When multiple males are present, they may engage in fights that can lead to injuries, including damage to the swim bladder.
  • Poor water conditions: Inadequate water conditions, such as extreme temperatures, incorrect pH levels, and fluctuating parameters, can compromise the functions of the swim bladder. Poor conditions not only impair the digestive process but also expose the fish to diseases that can affect the swim bladder.
  • Disease: The swim bladder is susceptible to bacterial and parasitic infections, which can cause inflammation.
  • Stress: Like all fish, neon tetras are sensitive to stress. Factors such as extreme temperatures, parameter fluctuations, and ammonia poisoning can subject them to high levels of shock and stress.
  • Swollen Organs: Swelling of organs due to cysts, tumors, or diseases can exert pressure on the swim bladder.

Also Read: Neon Tetra Swim Bladder Disease

2. Neon Tetra Sleeping Posture

When a fish assumes an upside-down posture and remains still, many people assume it is sleeping. However, this conclusion is not always accurate.

Fish, including neon tetras, do sleep. Since they lack eyelids, their eyes remain open while they rest. During this state of rest, they are less active but still alert to potential dangers.

Importantly, healthy neon tetras sleep in a right-side-up position. To determine whether your fish is sleeping or sick, observe its activity levels during periods of rest.

If the neon tetra stops moving when the lights are off and resumes swimming when the lights are turned back on, it was likely sleeping.

However, if it remains in an upside-down position during these rest periods, it indicates illness. A healthy neon tetra will stay right side up even while sleeping.

3. Your Neon Tetra Died

Fish, due to their composition of bones, protein, and fat, are slightly denser than water. Consequently, they neither sink nor float. But what happens when they die?

In most cases, a deceased fish will have gas trapped in its swim bladder. This gas causes the fish to float and appear upside down at the water’s surface.

If the neon tetra does not have any air in its swim bladder, it will sink to the tank’s substrate. However, as decomposition occurs, gas produced as a byproduct will cause the fish to float.

Death is the worst-case scenario, but fish die naturally. If your neon tetra is upside down and unresponsive to stimuli, even when removed from the aquarium, it has likely died.

Also Read: Why Is My Neon Tetra Floating At The Top?

What Should I Do If My Neon Tetra Swims Upside Down?

If your neon tetra is swimming upside down, it is either dead or suffering from swim bladder disease. If the fish is dead, remove it from the tank without waiting for scavengers to eat it.

Scavengers may ignore the remains, leading to the decomposition of the carcass and disrupting the water’s chemical balance.

If the neon tetra only floats upside down when sleeping, it is likely affected by swim bladder disease.

Fortunately, swim bladder disease can be reversed by identifying the underlying causes. Tailor the solution based on the specific cause:

1. Treating Swim Bladder Disease In Neon Tetras

Swim bladder disease can be addressed using various solutions and remedies, including:

  • Temperature Increase: Low temperatures can slow down digestion, so raising the temperature to 78-80 degrees Fahrenheit is recommended. If you have a heater, it won’t take long to achieve the desired temperature.
  • Fasting: If the fish is constipated, refrain from feeding it for three days. This allows the neon tetra time to digest the food already in its stomach. The fasting period helps shrink the expanded stomach due to constipation, aiding in recovery from swim bladder disease for some neon tetras.
  • Food: If the neon tetra remains sick after fasting, feed it cooked and peeled peas after the three-day fasting period. Peas are high in fiber and can alleviate constipation quickly.

When resuming the fish’s regular diet, avoid overfeeding. Feed the fish two to three times a day, providing only the amount of food it can consume within a few minutes.

Pre-soak the food, particularly flake food, to ensure it sinks before the fish eat it, preventing the ingestion of air.

  • Infections: If you suspect an infection caused swim bladder disease, consult a veterinarian. They will identify the responsible bacteria or parasite and recommend a suitable treatment. In the meantime, isolate the affected fish.
  • Conditions: Maintain a clean tank with appropriate pH levels and hardness.

Use water conditioners to remove chlorine, ammonia, nitrites, and other toxins. Neon tetras with physical injuries require a conducive environment for recovery.

2. Proper Feeding For Neon Tetras

If your neon tetra developed constipation due to overfeeding, learn from the experience and avoid repeating the mistake.

Consider installing an automatic feeder to ensure the fish is fed even when you are unavailable.

An automatic feeder dispenses food into the tank at the right time and in the correct amounts.

One recommended option is the Zoo Med BettaMatic Feeder (link to Amazon). It rotates every 24 hours, providing a daily feeding for your tetra. Ensure that the food pellets used are thin.

If you prefer not to use an automatic feeder, feed the neon tetra no more than twice a day, offering an amount of food it can consume within 2-5 minutes. Adjust the quantity until you find the right balance.

Both underfeeding and overfeeding can cause issues. If the neon tetras are fighting over food, it may indicate that the quantities provided are insufficient.

On the other hand, excessive leftovers indicate overfeeding.

3. Adjust Water Conditions For Neon Tetras

Maintaining the proper water conditions in the aquarium can accelerate the recovery of a sick, constipated, or injured neon tetra.

Ideal water parameters for neon tetras include:

  • Temperature: 76-81 degrees Fahrenheit
  • pH: 6.5-7.5
  • Hardness: 5-20 DH (70-300 ppm)
  • Ammonia: 0 ppm
  • Nitrites: 0 ppm
  • Nitrates: <20 ppm

Regularly test the water parameters using a testing kit. The API Water Test Kit (link to Amazon) is a reliable and cost-effective option.

Acclimate new neon tetras before introducing them to the tank to avoid subjecting them to sudden environmental changes that could lead to swim bladder issues.

4. Maintain a Clean Environment

Keeping the tank clean is crucial. Maintain nitrate levels below 20 ppm, while ammonia and nitrite levels should be at 0 ppm.

Most aquariums are equipped with filters, but it’s important to change the water regularly as well.

If the neon tetra is already swimming upside down, consider changing the water immediately to provide relief.

Avoid allowing leftovers and waste to accumulate in the tank, and regularly vacuum the substrate to prevent organic matter from rotting.

Keep water conditioners on hand to neutralize toxins like ammonia and chlorine.

The API TAP WATER CONDITIONER (link to Amazon) is a recommended option that helps prevent problems and provides immediate relief if ammonia levels spike unexpectedly.

5. Treat Potential Diseases

If your neon tetra exhibits symptoms such as rubbing against objects, fading colors, swollen eyes, reddened gills, raised scales, open sores, clamped fins, or the presence of spots, lumps, or cottony growths, it may indicate an infection.

In the case of swim bladder disease caused by bacterial infection, a veterinarian can identify the bacteria responsible by taking a sample of the fluid from the swim bladder using a needle.

Once the bacteria are identified, appropriate treatment can be recommended.

Avoid randomly treating the tank with antibiotics without proper diagnosis, as this can do more harm than good.

Also Read: Neon Tetra Swimming Vertically


Here is a brief summary of what I talked about above:

  • Neon tetras swimming upside down indicates swim bladder disorder caused by various factors like constipation, injuries, poor water conditions, diseases, stress, or swollen organs.
  • Treat swim bladder disease in neon tetras by adjusting temperature, fasting, feeding cooked peas, maintaining optimal water conditions, and addressing infections.
  • Proper feeding practices, like using an automatic feeder or small portions multiple times a day, prevent constipation and overfeeding in neon tetras.
  • Clean water conditions, regular changes, filtration, and water conditioners are crucial for neon tetras’ health and recovery from swim bladder issues.
  • Monitor for illness, adjust water parameters, and seek veterinary assistance to prevent and manage swim bladder disease and other health problems in neon tetras.