Why Are My Neon Tetras Dying? (With 5 Practical Solutions)

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I remember how frustrated I was when I noticed my very first neon tetra was dead. I carefully washed out the fish tank and all the gravel, but every few days, I would see another one of my neon tetras floating upside down at the top of the tank. Luckily, as time passed, I learned why this was happening.

Neon tetras usually die due to inappropriate water conditions, including pH, temperature, ammonia, nitrites, nitrates, and water hardness. However, in some cases, the fish was merely suffering from a parasitic infection, most commonly known as Neon Tetra Disease.

As we move forward, I will share five steps you should follow to ensure that your neon tetras will live longer and thrive in the tank. I will also include Youtube videos that will help you identify sick neon tetras and show you how to treat them.

Also Read: 15 Things You Should Know About Neon Tetras

Why Are My Neon Tetras Keep Dying?

People love neon tetras because they are small and colorful. If yours are dying, you have to find out why before you lose your entire neon tetra population. Sometimes, genetics are to blame.[1] Some neon tetras are deformed at birth, so you cannot do anything to help them.

In fact, you should encourage them to die out before they breed. Otherwise, they may pass those anomalies on to their offspring. But if genetic anomalies are not the cause of the numerous deaths in your neon tetra tank, you can blame the following:

1. The Water Isn’t Suitable For Neon Tetras

The water quality will impact the health of the neon tetras, determining how long they will live. Poor quality water can affect every creature in the tank, making them more vulnerable to diseases and encouraging them to die before their time. You have to keep the following in mind:

  • The Tank Wasn’t Cycled Properly

Aquariums that haven’t been cycled to completion are prone to spikes in ammonia and nitrates that will kill your neon tetras. New tanks are also dangerous, even if they have been cycled, because bacteria colonies that usually process contaminants are not properly established.

As such, even though the tank has been cycled to completion, ammonia and nitrates may continue to spike. This is why many aquarists encourage beginners to only add neon tetras to at least three to six months old tanks. This isn’t a rule. You don’t have to adhere to it. But older tanks are more stable and less likely to kill neon tetras.

  • The Wrong Water Parameters 

You have to keep the neon tetras in parameters that suit them. Pay close attention to the pH, temperature, and hardness. Besides inducing stress, the wrong parameters will make multiple neon tetras sick, killing them in the long run if you cannot treat them.

  • There Is No Stability

Neon tetras require stability. They will not respond well to tanks whose water chemistry keeps changing. You can create instability in a neon tetra’s aquatic environment by carrying out massive and frequent water changes. You need regular water changes to keep the tank clean. But frequent water changes will alter the tank’s chemistry. This will harm the neon tetras.

  • Poor Hygiene

If you cannot keep the neon tetra tank clean, you are going to expose your neon tetras to high concentrations of toxins like ammonia that can kill them. You may also introduce toxins like chlorine and lead to the tank by adding new water (during a water change).

2. Your Neon Tetras Are Stressed

While stress is an inconvenience to humans, it is deadly to neon tetras. If your neon tetras are always hiding, getting into fights, surfing the glass, laying still at the bottom of the tank, losing weight at alarming rates, and the like, they are stressed.

Stress has numerous sources, not just poor water conditions but a hostile environment filled with bullies, small tanks, overcrowding, underfeeding, and so much more. If your tetras present the signs above, I highly suggest following the steps below to fix the issue immediately.

3. The Tetras Were Overfed

Every beginner knows that underfeeding is bad. They understand that they have to feed their neon tetras on time and in sufficient quantities. But some of them do not realize that overfeeding is also harmful.

If you keep feeding your neon tetras more food than they need, not only will you attract ailments like bloating, constipation, and swim bladder disease, but the neon tetras are going to produce a lot more waste. That waste, along with the leftovers, will rot, destroying the balance you created in the water’s chemistry.

4. Your Neon Tetras Caught A Disease

One of the most prominent neon tetra illnesses is neon tetra disease, an ailment that the Microsporidian parasite causes.[2] Despite its name, neon tetra disease can afflict other types of fish, including angelfish, barbs, and rasboras.

It causes restlessness, discoloration, difficulty in swimming, and cysts, to mention but a few. Other notable neon tetra diseases that may kill your fish include columnaris, dropsy, hemorrhagic septicemia, mouth fungus, velvet, etc.[3]

Also Read: How Long Do Neon Tetras Live?

How Do You Keep Neon Tetras Alive?

As was mentioned above, you cannot help a neon tetra with genetic anomalies. This is also true for a neon tetra that is dying of old age. However, if you think that external factors caused your fish’s affliction, you can use the following methods to keep it alive:

1. Checking The Water Quality

If your neon tetras keep dying, I highly recommend that you start by improving the water quality. Depending on the health of the fish, you should consider adding some aquarium salt to keep infections at bay. But that isn’t enough. You have to keep the following in mind as well:

  • Testing – Keep testing kits on hand. Use them to keep an eye on the concentration of dangerous chemicals like ammonia and nitrates. You should also monitor the pH and temperature.

I personally use the API Freshwater Master Test KIT (link to Amazon). That bundle will accurately measure the ammonia, nitrates, nitrites, and pH in your tank. It also lasts for hundreds of measures, making it highly cost-effective.

These are the ideal water parameters for neon tetras:[4]

  1. Temperature: 75 to 80 degrees F.
  2. Water pH: 6.8 to 7.8.
  3. Ammonia, nitrites: 0 ppm.
  4. Nitrates: Below 20 ppm.
  5. Hardness: Between 2 to 10 degrees dH.
  • Tank Size – You need at least 20 gallons of water for a small school of neon tetras. If you are interested, here is an article I wrote on how many neon tetras should be kept in a fish tank.

Also Read: Neon Tetra Tank Size

  • Cycling – Try not to add neon tetras to brand-new tanks that you only recently cycled. Add other creatures first. Give the aquarium a few months to stabilize. Neon tetras are sensitive. You can also use the API Quick Start Nitrifying Bacteria (link to Amazon). That product will ensure that your water is ready to take in aquarium fish.
  • Oxygen – In many cases, a decent filter will prevent the oxygen levels from falling below acceptable levels by disturbing the water. But you should add air stones just in case. I use the Hygger Aquarium Air Stone Kit (link to Amazon), which is incredibly quiet.

Also Read: Do Neon Tetras Need A Bubbler?

  • Maintenance – Neon tetras eat once or twice a day. I also suggest giving them food they can finish in 2 minutes.[5] This will reduce the waste they produce and the number of leftovers. But you are still expected to clean the tank. That means vacuuming the substrate, occasionally scrubbing the hard surfaces, removing dead organisms, eliminating the algae, and performing water changes.
  • Filters – I highly suggest adding filters to the tank. An under gravel filtration system will not disappoint you. You can use other types. But avoid models with a strong inlet that could suck the neon tetras in. They are small fish.

Also Read: Do Neon Tetras Need A Filter?

2. Replacing The Water Properly

It is recommended to carry out regular water changes, but you shouldn’t do them frequently. Wait four days, possibly even a week. Keep them small, no larger than 20 or 30 percent. If your fish are already sick, you can use water conditioners to neutralize the toxins. 

Do this if you are worried that even a small water change will make things worse. Regardless of your maintenance techniques, it would help if you always kept the ammonia levels at zero and the nitrate levels under 20ppm.

3. Reducing Stress

If the neon tetras are stressed, and their tank is bare, you should add plants and decorations. They will provide hiding places. It is also essential to keep them in schools of 6 fish or more.[6] Keep them out of tanks with large, aggressive fish like Oscars and cichlids. They need friendly neighbors like harlequin rasboras, zebra danios, guppies, and dwarf gouramis.[7]

Also Read: Stress In Neon Tetras

4. Dealing With Diseases

As mentioned earlier, if your neon tetras seem sluggish, pale, skinny, and show no interest in food, they are very likely sick. If that is the case, you have to treat them. However, the treatment will depend on the disease. Keep the following in mind:

  • Keep the sick fish in quarantine.
  • Carry out water changes immediately. If the neon tetras are very sick, stick to small water changes of 10-15 percent. You can also use water conditioners, as I explained in this article.
  • Check the parameters. Sick neon tetras require optimal conditions, including the correct pH and temperature, to recover.
  • Consult a vet if you have failed to diagnose the symptoms of your fish.
  • You should know that some illnesses have no cures. That includes cancerous tumors, neon tetra disease, and hemorrhagic septicemia.[8] You have to euthanize the fish.

Also Read: 17 Neon Tetra Diseases & Their Treatments

If you’re interested, here is an excellent Youtube video that goes through the well-known Neon Tetra Disease and how to treat it. It also shows some excellent ways to prevent this condition from recurring:

It is worth mentioning that you shouldn’t buy fish that are already sick. Sick fish have signs and symptoms that are difficult to ignore, such as poor coloration, clamped or tattered fins, bulging eyes, bruises, cysts, sluggish movements, bloating, etc. 

If the neon tetra you want is surrounded by sick fish, that neon tetra is most likely sick. Do not assume that you have identified the only healthy neon tetra is a fish store aquarium filled with sick fish.

5. Starting A New Tank

If you suspect that your neon tetra died from an infection, you should consider replacing the water entirely. That is because the water itself might be carrying the disease. It would help if you also considered removing the objects in your tank, including plants, rocks, and decorations.

I typically recommend that step if you had a mass outbreak of neon tetra disease in your tank. However, that is not an easy decision to make. It is often said that you should not remove your aquarium plants. They will suck up the chemicals in the water and keep the parameters in check. 

But I don’t think it’s good to have plants where sick fish have died or become sick. I’d go so far as to say that removing plants and other decorations is a fact-of-life for most fish keepers.

Also Read: Neon Tetra Tank Setup

What Does A Sick Neon Tetra Look Like?

The most prominent sign for a sick neon tetra is irregular swimming. Sick tetras start surfing the glass (where they frantically swim up and down the aquarium wall), swimming in circles, crashing into objects in the tank, dragging their bodies across the substrate, etc.

Some neon tetras will become more erratic in their swimming. You will see them shooting wildly across the tank. Others will become sluggish. They will spend their days hovering in place or laying at the bottom.

If your neon tetra’s swimming behavior has not changed, look at the color. Some neon tetras may become darker. Others will become lighter. In extreme cases, depending on the disease, a neon tetra will develop cysts, bruises, and lumps all over its body. In some situations, the creature’s body will curve, revealing the curve that has formed in its spine due to its illness.

How Often Do Neon Tetras Die?

In the wild, neon tetras can live for ten years. But in a tank, their lifespan rarely exceeds three years. A neon tetra can stay alive for all three years if it is treated well. But it can die in hours if you introduce it to a tank with atrocious conditions. 

Many people think that neon tetras are hard to keep and maintain. But the truth is that they are pretty straightforward to care for. Also, neon tetras are reactive fish, meaning they will show signs of illness as soon as their environment becomes too challenging for them. So you’ll know if something went wrong.

Also Read: Do Neon Tetras Sleep?


Neon tetras are one of the most popular freshwater aquarium fish for beginners to start with. However, sometimes they fail to survive. This happens too often, and it doesn’t have to be this way. The tips I have provided should help you to keep your neon tetras alive and well. 

Do not follow them blindly. Evaluate them, and adapt them according to your unique set-up, your aquarium’s filtration system, the compatibility of the fish you want to introduce, etc. I believe that you will find out that neon tetras can stay alive if you take good care of them properly.


  1. https://tetra-fish-care.com/why-are-my-neon-tetras-dying-symptoms-and-prevention/
  2. https://www.thesprucepets.com/neon-tetra-disease-1378484
  3. https://tetra-fish-care.com/tetra-fish-diseases-and-treatments/
  4. https://www.aqueon.com/information/care-sheets/tetras
  5. https://tetra-fish-care.com/how-much-neon-tetra-eat/
  6. https://kidadl.com/animal-facts/neon-tetra-facts
  7. https://modestfish.com/neon-tetra-tank-mates/
  8. https://modestfish.com/fish-disease-guide/