Neon Tetra Swimming Vertically: 6 Quick Solutions

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Many times I see bizarre swimming behaviors in my tank. For example, more than once, I caught my neon tetra swimming vertically. As the years passed, I learned why this issue occurs and how to deal with it. Now, I am willing to share my experience.

Neon tetras tend to swim vertically due to a swim bladder disorder, compromising the fish’s buoyancy. In this case, the tetra will struggle to maintain a normal swimming position and possibly sink to the bottom. However, tetras also swim head up when stressed, primarily due to low water quality.

As we move forward, I will list a few more reasons that might have forced your tetra to swim vertically with its head up. I will also share six crucial steps you should take to solve that issue, including using the API Aquarium Test Kit (link to Amazon) to measure the water parameters.

Why is my Tetra Swimming Vertically?

Neon tetras shouldn’t swim vertically. This isn’t normal behavior for them. More importantly, you shouldn’t ignore it. Sometimes, vertical swimming is temporary, the result of a mild problem. Other times, the habit is a symptom of a more serious issue, in which case, you need to resolve it before your neon tetra suffers lasting harm.

Some of the most common causes of vertical swimming in neon tetras include:

1. Your Tetra is Sleeping

Like most fish, neon tetras sleep. Like various shoaling fish, neon tetras tend to remain in motion as they rest, though their movements in this state are slower and more sluggish. You cannot always predict the position they will assume when they sleep.

Some neon tetras have been known to hover vertically in the water near the gravel.[1] If you are new to aquariums and you don’t know that fish can remain in motion while they sleep, you might not realize that your neon tetras are sleeping rather than actively swimming.

One way of diagnosing this issue is to identify the time of day when your neon tetras appear to swim vertically. If you only notice this behavior at night or when the lights are off, you have every reason to conclude that the fish are sleeping.

2. The Tatra Suffers From Constipation

Neon tetras may swim vertically because they overate. You can tell by looking at their bellies, which are distended in such cases. Overfeeding in scenarios like this isn’t so bad. While the bloating might prevent the fish from swimming correctly for a while, you can wait for the problem to resolve itself in a few hours. 

You won’t be so lucky if the neon tetra in question is constipated. Constipation is as common in fish as it is in humans. It can happen as a result of a poor diet, low-quality food, and overfeeding.[2] It can also affect a fish’s ability to swim. A constipated fish looks fat and has a swollen stomach. As you might expect, it doesn’t eat as much.

Also Read: Why Is My Neon Tetra Fat And Bloated?

3. Your Tetra Swallowed Air

Some people always blame bloating on overfeeding and constipation. However, this isn’t always the case. A fish may swallow air as it feeds, especially if it is eating from the surface.[3] This can lead to bloating. As with constipation, the condition can affect the fish’s ability to swim properly. Like overeating, it can also resolve itself given enough time.

4. Swim Bladder Disease

The swim bladder is an organ that fish use to remain upright. Neon tetras, like other fish, use it to control their buoyancy. Swim bladder disease is an illness that occurs when the swim bladder malfunctions. 

Once this happens, the fish will manifest strange swimming habits because it doesn’t have as much control over its movement in the water as it once did. If your neon tetra is swimming vertically, with the head up and the tail down, swim bladder disease should be one of the first factors you consider. 

After all, no other organ affects a fish’s ability to swim as directly as the swim bladder. Swim bladder disease has a variety of causes, including bacterial and parasitic infections and poor water quality. The illness can also manifest as a result of injuries and birth defects.[4]

Also Read: Neon Tetra Swim Bladder Disease

5. Elevated Aquarium Toxins

Neon tetras are vulnerable to several toxins. Ammonia is one of the most problematic because it grows in concentration as a result of poor maintenance. Even though nitrites are less toxic, they can also compromise your neon tetra’s health.

Most aquarists are experienced enough to keep an eye out for chlorine. But some of them do not appreciate the dangers associated with chlorine poisoning, which include gill tissue necrosis and hypoxia. A fish in a tank with chlorine will have trouble swimming.[5]

If it survives the presence of chlorine, you are bound to observe strange behavior such as vertical swimming. Some fish will turn upside down. Other toxins that may affect your neon tetra’s swimming habits include carbon dioxide and hydrogen sulfite.

Also Read: Why Is My Neon Tetra Swimming Upside Down?

Hydrogen sulfite is less of an issue because it is easy enough to detect. If you smell your aquarium, you will catch the scent of rotten eggs.[6] Chlorine isn’t as easy to detect, which is why it is bound to slip the attention of some aquarists.

6. Low Water Quality

Toxins are not the only elements that affect the quality of your water. If you cannot replicate the same conditions to which the neon tetras are accustomed in the wild, they will respond to the stress by manifesting bizarre symptoms such as vertical swimming.

Your tank requires soft water with the proper pH and temperature. Neon tetras also expect stability. They do not appreciate aquariums in which the temperature and pH are constantly changing, mainly due to massive water changes.

7. Your Tetra is New to the Tank

If your tetra is new to the tank and failed to acclimatize, then vertical swimming is just one sign of stress among many that you may notice as a result. Fish do not appreciate drastic changes, and that is what they encounter whenever you move them from one tank to another without proper acclimation. The shock they experience can lead to death.

How to Treat Neon Tetras That Swim Vertically?

Neon tetras that swim vertically are not a lost cause. You can use the following steps to eliminate the habit:

1. Adjusting the Aquarium Conditions

I highly suggest creating a conducive environment for your neon tetras. That means making sure that their aquarium is fully cycled. You should also maintain the proper temperature (70 to 78 degrees F) and pH (6.0 to 7.0).[7]

For that purpose, I genuinely recommend getting the API Aquarium Test Kit (link to Amazon). That bundle allows you to accurately measure the pH, ammonia, nitrates, and nitrites in your tank. Within five minutes, you’ll know if the water has to be replaced.

Even though people with the right weather can live without one, you are encouraged to use a heater. This will prevent the temperature in the aquarium from shifting wildly.

Neon tetras need a minimum of 20 gallons depending on the number of fish you have. Overstocking and overcrowding can exacerbate their stress, not only making their vertical swimming worse but potentially killing them in the long run.

2. Treating Swim Bladder Disease

The treatment you use to combat swim bladder disease will depend on the factors that caused it. For instance, you can fight infections using antibiotics. That is usually recommended if your tetra also appears lethargic and pale. Please consult a vet to adjust the proper medication.

However, if overfeeding and constipation are the problem, you can handle it on your own. Place the neon tetras on a fast for three days before feeding them cooked and peeled peas. The food item will improve their digestion.

Here is a short Youtube video that describes how to do that:

Some aquarists will encourage beginners to raise the temperature by a few degrees. Others will prescribe salt baths for bacterial illnesses. Of course, these treatments will only work if an external element caused the swim bladder disease. They won’t work if your neon tetras have a birth defect.

If you are unsure what caused your tetra to suffer from a swim bladder disease, I suggest getting the API AQUARIUM SALT (link to Amazon). Put the sick fish in a hospital tank and pour one tablespoon for each gallon of water. That could be added to the other suggestions above.

3. Ensuring Proper Maintenance

The easiest way to prevent toxins from accumulating is to maintain your tank. That means carrying out regular water changes, removing waste and leftovers, increasing aeration, and vacuuming the gravel.

If you can keep the tank clean, you don’t have to worry about ammonia, nitrites, carbon dioxide, and hydrogen sulfite. Toxins that come from outside the tank, such as chlorine, chloramine, and copper, can be removed using water conditioners.

For instance, to neutralize chlorine and chloramines, I use the API TAP Water Conditioner (link to Amazon). That product is pretty easy to use. All you have to do is add 1 ml (using the bottle’s cup) for every 20 gallons of aquarium water. It will also take care of zinc, copper, and lead found in most tap water supplies.

4. Adding a Few Plants

Like most fish, neon tetras prefer to live in tanks with an abundance of hiding places. Add fast-growing plants like Aponogetons that will put your fish at ease. They will also appreciate the presence of caves, pots, rocks, driftwood, and the like.

You can apply as much creativity as you want in the design of your aquarium’s environment. However, you shouldn’t add so many plants and decorations that they crowd the tank. As long as your tetras got places to hide, they are less likely to swim vertically out of stress.

5. Picking the Right Tankmates

Neon tetras are peaceful shoaling creatures that should be kept in groups of 20 or so fish. Isolated neon tetras are more likely to succumb to stress, which can lead to vertical swimming. 

I also suggest providing them with companions. Neon tetras that live in groups are calmer and happier. When it comes to finding them tankmates from other species, prioritize peaceful fish of a similar size, including guppies, mollies, cardinal tetras, and cory catfish.[8]

6. Allowing Proper Acclimatization

Try not to add new neon tetras to a tank without acclimatizing them. You can do this by placing them in a bag filled with water from their old tank and then floating the bag in the new tank for a quarter of an hour.

This will allow them to adjust to the temperature. You can also use the drip method to add water from the new tank to the bag, allowing the tetras to grow accustomed to the new conditions.

How Can You Tell if a Neon Tetra is Stressed?

These signs indicate that a neon tetra is stressed:

  1. The fish will lose its appetite; it either won’t eat, or its food intake will drop dramatically
  2. It will start swimming erratically. This could mean swimming upside down, flitting around the tank, crashing into the decorations, and glass surfing.
  3. Stressed neon tetras may disappear altogether. Because they don’t feel safe out in the open, they will start spending every waking moment in hiding.
  4. Neon tetras could respond to stress by becoming aggressive. They will attack fish of the same or smaller size, nipping at their fins and making life very difficult for them
  5. Stressed neon tetras will start frequenting the surface where they will gasp for air even though their tank has plenty of oxygen.

If you notice these signs in your tetra, I highly suggest isolating the sick fish. If a bacterial or viral infection caused the phenomenon, it may quickly spread across your tank and infect other fish. Then, your next best step would be consulting an aquatic veterinarian.


If you found your tetra swimming vertically, it requires your attention. That is usually a sign that the fish is suffering from a swim bladder disorder, compromising its buoyancy. In this case, please isolate the sick fish and elevate the temperature by a few degrees.

Then, let your tetra fast for three days. Following that, you may feed your tetra with cooked, pilled peas. You should also check the water parameters. In many cases, elevated toxins stress aquarium fish, forcing them to swim head up in an attempt to escape.