Why Do My Neon Tetras Stay At The Bottom Of The Tank?

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Seeing your neon tetras swimming consistently at the bottom of the tank raises many questions and for a good reason.

When I first saw this behavior in my fish I had no idea what causes this or what to do. Fortunately, over the years, I gained some experience in this topic.

In this article, I will walk you through the reasons that might be driving your neon tetras to stay at the bottom and offer some useful solutions for this situation.

Let’s get started.

Are Neon Tetras Bottom Dwellers?

No, neon tetras are not naturally bottom dwellers. They typically swim in the middle layer of the water in their tank.

If a neon tetra is frequently staying near the bottom, it may be a sign of stress, illness, or other unfavorable conditions.

Reasons Your Neon Tetras Staying At The Bottom Of The Tank

If your neon tetras consistently swim at the bottom, there are a few things to keep in mind:

1. Extreme Temperature Discomfort

If the water’s temperature deviates from their comfort zone, neon tetras might react by staying at the bottom of the tank:

  • Tropical Habitat: Neon tetras originate from warm, tropical climates. The optimal water temperature for these fish is between 70-81°F (21-27°C).
  • Lower Metabolic Rate: When the water temperature drops, neon tetras’ metabolic rates decrease, leading to lethargy and potentially causing them to stay at the bottom.
  • Temperature Shock: A sudden change in temperature, either up or down, can induce temperature shock in neon tetras. This stress can force them to retreat to the bottom of the tank.
  • Lack of Oxygen: Higher temperatures reduce the oxygen levels in the water. Neon tetras, struggling to breathe, might stay lower in the tank where the temperature is usually cooler.
  • Body Functions Impairment: At extreme temperatures, the bodily functions of neon tetras may be impaired, prompting them to stay at the bottom to conserve energy.

2. Poor Water Quality

Water quality is a significant determinant of any fish’s health, including neon tetras. Poor water quality can cause stress, leading them to hide or stay at the bottom of the tank:

  • Ammonia and Nitrite Toxicity: High levels of ammonia or nitrite in the tank are toxic for neon tetras and can cause them to seek refuge at the tank bottom.
  • Improper pH Levels: Neon tetras prefer slightly acidic water (pH 5-7.5). If the pH shifts significantly, it can result in discomfort for the fish, leading them to stay low in the tank.
  • High Chlorine Content: If the water contains high levels of chlorine or chloramine, it can harm neon tetras and push them to stay at the tank’s bottom.
  • Poor Filtration: Inadequate or ineffective filtration can lead to a build-up of waste materials, making the water quality poor and stressing neon tetras.
  • Lack of Water Changes: Regular water changes are necessary to keep water parameters stable. Infrequent changes can cause water quality to deteriorate, stressing the neon tetras.

3. Incompatible Tank Mates

Just like humans, neon tetras also need to feel safe and secure in their surroundings. 

Introducing incompatible tank mates can disrupt their peace, causing them to hide at the bottom:

  • Aggressive Species: If the tank houses aggressive species, neon tetras might feel threatened and retreat to the tank’s bottom for safety.
  • Size Differences: Tank mates significantly larger than neon tetras can be intimidating, causing the smaller fish to hide.
  • Territorial Behavior: Some fish species are territorial and might stress the peaceful neon tetras, pushing them to the bottom of the tank.
  • Overcrowding: Overcrowding can lead to increased competition for resources, which can stress neon tetras, causing them to stay at the tank bottom.
  • Feeding Conflicts: If tank mates outcompete neon tetras for food, they might retreat to the tank bottom out of stress or hunger.

Also Read: Why Do My Neon Tetras Keep Hiding?

4. Struggling With A Severe Disease

Disease and illness are unfortunately common reasons why neon tetras might be found at the tank’s bottom. They may seek refuge there when feeling unwell:

  • Infectious Diseases: Neon tetras might suffer from bacterial, viral, or fungal infections, which can weaken them and push them to stay at the bottom.
  • Parasitic Infestations: Parasites can lead to a significant decrease in the health and energy of neon tetras, causing them to retreat to the tank bottom.
  • Neon Tetra Disease: This specific disease, affecting neon tetras, causes the fish to lose color and can lead them to seek the perceived safety of the tank bottom.
  • Organ Failure: Serious conditions like organ failure can weaken neon tetras considerably, causing them to stay at the bottom of the tank.
  • Old Age: Aging neon tetras may suffer from various ailments, leading them to rest at the tank’s bottom.

5. High Levels of Stress

Stress is detrimental to the health of neon tetras. High stress levels can result in unusual behavior, such as staying at the bottom of the tank:

  • Inappropriate Lighting: Neon tetras prefer subdued lighting. Excessively bright or irregular light cycles can stress them out.
  • Excessive Noise or Vibrations: Loud noises or constant vibrations around the aquarium can stress neon tetras, making them retreat to the bottom.
  • Handling Stress: Neon tetras might become stressed due to frequent handling or during tank cleaning.
  • Lack of Hiding Spaces: If there aren’t enough plants or decorations for hiding, neon tetras can feel exposed and stressed.
  • Sudden Environmental Changes: Any abrupt changes in the tank environment can lead to stress, forcing neon tetras to stay at the tank’s bottom.

Also Read: Stress In Neon Tetras

6. Inadequate Number Of Neon Tetras

Neon tetras are schooling fish that feel safe and comfortable when in groups. An inadequate number of neon tetras in a tank can cause stress, making them stay at the bottom:

  • Loneliness: A single neon tetra or just a few may feel lonely, stressed, and unsafe, causing them to stay at the tank’s bottom.
  • Inadequate Schooling: A school of less than 6-10 neon tetras might not offer the security these fish need, causing stress and bottom-dwelling behavior.
  • Loss of School Members: If the school’s numbers suddenly decrease, it may stress the remaining neon tetras, making them retreat to the tank bottom.
  • Breaking School Structure: If something disrupts the schooling structure of neon tetras, it can cause stress and bottom-dwelling behavior.
  • Lack of Swimming Space: If there isn’t enough space in the tank for the school to swim freely, neon tetras can become stressed and retreat to the tank’s bottom.

How To Treat Neon Tetras That Stay At The Bottom

Treating neon tetras that swim at the bottom of the tank typically involves the following:

1. Treating Temperature Discomfort

Maintaining a stable and suitable temperature for neon tetras is crucial. Here’s how you can fix temperature discomfort:

  • Install an Aquarium Heater: If the water is too cold, install a heater to maintain the water temperature within the range of 70-81°F (21-27°C) that neon tetras prefer. My recommendation: Orlushy Submersible Aquarium Heater (link to Amazon).
  • Use a Thermometer: Regularly monitor the water temperature with an aquarium thermometer to avoid extreme fluctuations that could stress neon tetras.
  • Gradual Temperature Changes: If the temperature needs adjustment, do it gradually over several hours to prevent temperature shock.
  • Provide Oxygen: In warmer temperatures, ensure adequate oxygen supply with an air pump or by creating surface water movement to avoid stressing your neon tetras.
  • Proper Tank Placement: Place the tank away from direct sunlight, windows, and air vents to prevent sudden temperature changes.

Also Read: Neon Tetra Temperature

2. Fixing Poor Water Quality

Ensuring good water quality is essential for the well-being of neon tetras. Here’s how to tackle water quality issues:

  • Regular Water Changes: Perform regular partial water changes (20-30%) weekly to keep the water parameters stable for neon tetras.
  • Water Testing: Regularly test the water for ammonia, nitrite, nitrate, and pH levels. Any significant changes could cause stress to neon tetras. I do that with the API FRESHWATER MASTER TEST KIT (link to Amazon).
  • Proper Filtration: Ensure the tank has a good filtration system to remove waste and keep the water clean.
  • Use Water Conditioner: If using tap water, add a water conditioner to neutralize harmful chlorine and chloramine. My recommendation: Tetra AquaSafe Plus (link to Amazon).
  • Maintain Proper pH: If the pH levels are not optimal for neon tetras (pH 6.0-7.0), use pH adjusters cautiously to correct it.

Also Read: What Is The Best pH Level For Neon Tetras?

3. Dealing with Incompatible Tank Mates

For a peaceful environment for neon tetras, addressing issues with incompatible tank mates is necessary:

  • Choose Compatible Species: House neon tetras with peaceful, similarly sized species to prevent bullying.
  • Avoid Overcrowding: Ensure the tank is large enough to accommodate all the fish without overcrowding, reducing stress for neon tetras.
  • Monitor Fish Behavior: Regularly observe the behavior of all fish. If any fish is showing aggressive behavior, it might be necessary to move it to a different tank.

When it comes to neon tetras, I would avoid aggressive and large fish like:

  • Oscar (Astronotus ocellatus)
  • Red Devil Cichlid (Amphilophus labiatus)
  • Jack Dempsey (Rocio octofasciata)
  • Green Terror (Andinoacara rivulatus)
  • Convict Cichlid (Amatitlania nigrofasciata)
  • Jaguar Cichlid (Parachromis managuensis)
  • Flowerhorn Cichlid (Hybrid cichlid)
  • African cichlids (various species, such as Mbuna cichlids from Lake Malawi)

Instead, I would stick to more peaceful and docile species like:

  • Harlequin Rasbora (Trigonostigma heteromorpha)
  • Cardinal Tetra (Paracheirodon axelrodi)
  • Glowlight Tetra (Hemigrammus erythrozonus)
  • Ember Tetra (Hyphessobrycon amandae)
  • Celestial Pearl Danio (Danio margaritatus)
  • Endler’s Livebearer (Poecilia wingei)
  • Pygmy Corydoras (Corydoras pygmaeus)
  • Cherry Barb (Puntius titteya)

Also Read: 19 Great Neon Tetra Tank Mates

4. Handling Neon Tetras Struggling With A Severe Disease

Sick neon tetras require immediate attention. Here are ways to manage diseases:

  • Quarantine Sick Fish: If a neon tetra is showing signs of disease, move it to a quarantine tank to prevent the spread of disease.
  • Consult a Vet: Seek advice from a veterinarian experienced in fish diseases to diagnose and treat the neon tetra.
  • Proper Medication: Use the prescribed medications to treat the disease.
  • Maintain Water Quality: Keeping the water clean and at the right parameters can aid in the neon tetra’s recovery.
  • Observation: Regularly observe the neon tetra’s behavior and signs of improvement or worsening conditions.

Also Read: 17 Neon Tetra Diseases & Their Treatments

5. Reducing High Levels of Stress

Creating a calm and suitable environment for neon tetras is key to reducing their stress. Here’s what you can do:

  • Maintain Regular Light Cycles: Neon tetras need periods of darkness to rest. Ensure the lighting imitates natural day-night cycles.
  • Noise Control: Minimize loud noises and vibrations near the aquarium to reduce stress.
  • Minimize Handling: Handle neon tetras only when necessary and be gentle during tank cleaning.
  • Provide Hiding Spaces: Ensure the tank has plenty of hiding spots, like plants and decorations, for neon tetras.
  • Stable Environment: Avoid sudden changes in the tank environment, such as temperature or pH shifts, to prevent stress.

Also Read: Why Is My Neon Tetra Not Moving?

6. Adjusting The Number Of Neon Tetras

Since neon tetras are schooling fish, they prefer to be in groups. Here are ways to manage their numbers:

  • Increase Their Numbers: Neon tetras should be kept in groups of at least 6-10. If you have fewer, consider getting more to reduce stress.
  • Prevent Sudden Changes: If you need to add more neon tetras, introduce them gradually to the tank to avoid startling the existing fish.
  • Provide Enough Space: Make sure the tank is large enough to accommodate the school, allowing the neon tetras to swim freely.
  • Keep Close Watch: Regularly observe the school to check for any signs of stress or discomfort.


Neon tetras are not bottom dwellers, which is why catching them swimming at the bottom of the tank the entire tank should raise a concern.

There are numerous reasons behind that issue, starting with inappropriate water conditions, inaccurate temperature, stress, and diseases.

If you are not sure what is going on with your neon tetras, I highly suggest consulting an expert. Aquatic vets will guide you fast and provide the right treatment.