Fish in general are a pet that is most prone to die.  The neon tetra is one of the most popular fish for an aquarium due to its ease-of-care and vibrant colors of red, blue, and translucent. 

 They only grow to about 1.5 inches and have a peaceful temperament.  They are a freshwater fish found originally in the Amazon jungles.  Today, each month around 2 million neon tetra fish are sold for home aquariums. 

 They should be kept in schools of approximately 15 fish.  There are a variety of reasons for a neon tetra to die such as sudden changes in the water temperature and conditions.

Why Are Your Neon Tetras Dying?

 In addition to sudden changes in the temperature and condition of their water, there is also a disease that can cause this fish, and other fish to die.  It is called the neon tetra disease.  It is deadly to many species of fish.  It is not contagious to humans.

  • Cause:  It is caused by an organism that will leach the life out of the fish until the fish dies.  
  • Symptoms:  There are many symptoms for this disease, including growing white cysts or bumps all over their body, losing their color until the fish is an opaque pale white color.  They will lose all their energy and make them have the inability to not swim right.  They will start to swim erratically, act restless, and not swim with the other fish.
  • Cure/Treatment:  There is no 100% effective cure and no medication to slow the progress of the disease.  It is best if you euthanize the fish to keep them from suffering a painful death.
  • Infectious to Other Fish:  Yes, it is infectious to other fish so you need to remove them from the aquarium quickly when you notice another fish sick or dead from this disease.  
  • How Spread:  This disease is spread by the dead fish and can make the aquarium contagious.  The parasite will enter the fish through their mouth and then bind to the stomach along with the digestive system.  It slowly kills the fish from the inside out.  The other fish can get this parasite by eating all or part of the dead fish if it is not removed.  This is how the disease can spread quickly.
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tetras in aquarium

Symptoms of a Dying Neon Tetra

1. Stress

This is usually the first symptom that you will see in a dying neon tetra.  There are a lot of things that can cause stress besides a disease.  This is the first thing that a neon tetra will experience if the aquarium conditions change and changes in water chemistry. 

Make sure that the water is clean because otherwise, unclean water can lead to bacteria infecting the fish with different diseases.  Bacteria can make the water very toxic due to the ammonia level in the water, food remains, and fish wastes. 

The ammonia cannot only stress your neon tetra out but can also kill them in a matter of days.  If you have a fish that has died in your aquarium, you need to move the healthy ones out, clean out the aquarium, and purify the water.  Also, watch to see if any other fish are getting stressed as they could be getting sick.

2. Restless Neon Tetra

When the neon tetra does not act like its energetic playful self, but restless, this is could mean they are sick or dying.  Do not automatically assume they are sick or dying if they are acting restless because other things can make them restless. 

For example, when you first introduce them to their new home they might become restless because of new surroundings and possible new aquarium mates.  Do keep an eye on them because sometimes they cannot adapt to their new habitat and just die.  

One way to avoid this is to slowly introduce them to their new aquarium is to let the bag of neon tetras that you got from the breeder or pet store to just float on the water so they will get used to it.  Once they seem okay with it, you can slowly let some of the aquarium water come into the bag every five minutes for an hour, and then you can slowly release them into the aquarium.  Doing it this way will be less stressful for them.

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sad neon tetra

3. Not Raising Itself in Water

If you find your neon tetra swimming at the bottom of the aquarium and then they are not trying to raise themselves in the water, they could be sick.  You may also find your neon tetra floating at the surface and unable to swim at the bottom of the aquarium. 

Both of these situations can indicate that there is something wrong with your neon tetra.  To prevent any problems you should move the fish that is sick into another small aquarium and watch them for 24 hours to see if it changes its swimming behavior. If it does not, then you should not put it back into the aquarium with the other fish.

4. Swimming in Abnormal Patterns

Normally the neon tetras will swim in fixed patterns, which you will notice as you watch them.  Soon you will get used to their synchronized swimming.  When you notice any strange patterns this should be an alarm something is wrong.  It is a sign of stress and a sign that they are not following their school and that it could be sick and on the verge of dying. 

At this time you need to check the aquarium to make sure that the water conditions and temperatures are correct along with checking out the lighting.  They could also be bullied by another aggressive fish in the aquarium or maybe the school is not accepting them for some reason. 

Watch and observe your fish to find out the reason for them to be swimming in an abnormal pattern.

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  • The causes of your neon tetra dying can range from Neon Tetra Disease to the water conditions and temperature.
  • Observe your fish if you notice any odd behavior or irregular swimming patterns.
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Hi! I'm Anna and I´m a certified cynologist (KAU, ACW). Expert, blue cross volunteer, owner of Chinese crested kennel "Salvador Dali" and breedless friend called Fenya. "I can't imagine my life without dogs and I totally support the idea #AdoptDontShop".