It’s not good if your tetras swim sideways, and it isn’t typical behavior for them to do so.

Sideways swimming is sometimes the consequence of a minor ailment. This habit may occasionally be a symptom of a more severe problem. You should address it before your neon tetra gets harmed.

The following are some of the most frequent reasons for neon tetra vertical swimming:

  1. Your Tetra is Sleeping

Neon tetras, like many other fish, sleep. They move less and slower as they rest, although their activities are still somewhat faster than average.

So, suppose you’re unfamiliar with aquariums and don’t know that fish can swim while they sleep. In that case, you may not realize that your neon tetras are sleeping rather than actively swimming.

The time of day when your neon tetras seem to swim sideways is a method of diagnosing this condition.

If you only notice this behavior at night or when the lights are off, there’s no reason to doubt that the fish are sleeping.

You can’t always predict how they’ll settle down when they sleep. Some neon tetras rise vertically in the water near the grave while sleeping.

  1. The Tatra Suffers From Constipation

Neons may swim up because they have fed too much. You can tell by looking at their bellies bloated in such situations.

While the bloating may restrict the fish’s swimming for a time, you can wait for the issue to go away on its own in a few hours.

If the neon tetra is constipated, you will not be so fortunate. Constipation is just as prevalent in fish as it is among humans.

It May Be a Result of:

  • A poor diet
  • Low-quality food
  • Overfeeding

So, it would help if you changed your neon’s diet because it may affect the other fish in the tank.

  1. Your Tetra Swallowed Air

Bloating is sometimes blamed on overeating or constipation. This isn’t always the case, though.

Air may be inhaled by a fish while feeding, especially if eating from the top. Bloating can result as a result of this.

The disorder may impede a fish’s ability to swim correctly. However, you can treat it by simply giving it enough time away.

  1. Swim Bladder Disease

The swim bladder is a fish organ that allows them to stay upright. Like other fish, neon tetras employ it to regulate their buoyancy.

This disease is an ailment in which the swim bladder malfunctions.

When a fish becomes unstable, it loses control over its movement in the water, and strange swimming behaviors may appear. 

If your neon tetra is swimming sideways, with the head up and the tail down, swim bladder disease should be one of your first considerations.

After all, the swim bladder is the only organ that affects a fish’s ability to swim as directly as it does.

 Swim Bladder Disease Has a Variety of Causes, Including:

  • Bacterial infections
  • Parasitic infections
  • Poor water quality
  • Injuries
  • Congenital disabilities
  1. Elevated Aquarium Toxins

Neon tetras are vulnerable to several toxins. When they are high enough, toxins in your aquarium can kill your neon tetras.

Some of These Toxins Are:


Ammonia is one of the most dangerous toxins to fish. It is the product of decaying organic matter and builds up quickly in an aquarium.

If you have high ammonia levels in your tank, it will quickly poison your fish since it will deprive them of oxygen.

So, the presence of ammonia in your tank will lead your fish to swim unusually.


Nitrite is less common than ammonia but can also be deadly to fish. It’s produced when bacteria break down ammonia.

Don’t be surprised if your fish start swimming erratically when nitrite is present in your tank.


Nitrate is the least toxic of the three and is produced when nitrite breaks down.

While not as immediately harmful as ammonia or nitrite, it can still produce toxic levels, leading your tetra fish to swim sideways.


Some novices aquarists don’t know that chlorine is a toxin to fish, and it’s present in most tap water and can be deadly at high levels.

Chlorine poisoning can lead to gill tissue necrosis and hypoxia, both dangerous.

If chlorine is excluded, you may expect weird behavior like vertical swimming. Some fish will flip upside down.

Carbon dioxide

Carbon dioxide (CO2) is a gas that is heavier than air. When it accumulates in water, it can suffocate fish.

CO2 is produced when organic matter decomposes. You can often see it bubbling out of the water if there’s an abundance.

If you see your neon tetras swimming at the surface and gasping for air, CO2 may suffocate them.

Hydrogen sulfite

Because hydrogen sulfite is easier to detect, it is a less severe issue. If you take a whiff of your aquarium, there will be a rotten-egg odour.

This gas is toxic to fish and will cause them to have problems swimming.

  1. Low Water Quality

Toxins are not the only substances that can harm your water quality.

If you can’t replicate the circumstances to which neon tetras are accustomed in the wild, they will stress and exhibit abnormal symptoms such as vertical swimming.

Your tank requires soft water with the correct pH and temperature levels. Neons also want a consistent environment.

They do not appreciate aquariums with a temperature and pH that are constantly changing, mainly when you make significant water changes.

  1. Your Tetra is New to the Tank

If your tetra is new to the tank and failed to acclimate, vertical swimming is just one sign of stress among many that you may notice as a result. 

Fish dislike abrupt changes, so they are so delicate to move from one tank to another without allowing time to adjust. The shock they receive may be lethal.

How to Treat Neon Tetras That Swim Sideways?

The following are several ways you can do so:

  1. Adjust the Aquarium Conditions

Water PH

We recommend maintaining a neutral pH of 6.0 to 7.0 in your tank.

We strongly recommend getting the API Aquarium Test Kit (link to Amazon) for that purpose. 

This bundle can measure your tank’s pH, ammonia, nitrates, and nitrites. You’ll know if the water has to be changed after just five minutes.

Water Temperature

It would help if you kept the tank’s temperature at about (70 to 78 degrees Fahrenheit)

We recommend investing in a good aquarium heater cause it will help maintain your tank temperature and keep your fish healthy.

Tank size

The best tank size for neon tetras is 20 gallons, depending on the number of fish in the tank.

Overstocking and crowding can exacerbate their stress, making their sideway swimming worse and potentially causing their deaths in the long run.

So, getting a big enough tank for your fish is essential.

  1. Treat Swim Bladder Disease

The treatment you choose to cure swim bladder disease is determined by the reasons that caused it. Antibiotics, for example, may be used to treat infections.

However, if overfeeding and constipation are the problem, you can resolve them independently.

Place the neon tetras on a fast for three days before feeding them with cooked and peeled pears. The foodstuff will aid the digestion of your fish.

Many hobbyists advise beginners to raise the temperature by a few degrees to help prevent illness.

On the other hand, bacterial infections may be treated with salt baths, and we suggest getting the API AQUARIUM SALT.

Pour one tablespoon for each gallon of water into a hospital tank with the sick fish.

Of course, these therapies will only be effective if an external factor is to blame for the swim bladder disease. They won’t help if your neon tetras are born with a defect.

  1. Ensure Proper Maintenance

The most straightforward approach to keeping poisons at bay is regularly cleaning your tank.

To keep your tank clean, you must do Regular water changes, remove waste, and leftover removal, increase your tank aeration, and vacuum the gravel.

Also, you can use water conditioners to remove chemicals that enter the tank from the outside, such as chlorine, chloramine, and copper.

We recommend the API TAP Water Conditioner to remove chlorine and chloramines.

It is pretty simple to use. Add one millilitre (using the bottle’s cup) for every 20 gallons of aquarium water. It will also eliminate zinc, copper, and lead from most tap water sources.

  1. Adding a Few Plants

Neon tetras, like other fish, prefer living in tanks with lots of hiding places.

So, when creating your aquarium’s environment, you may use as much imagination as possible.

Fast-growing plants like Aponogeton will allow your fish to relax, so you’ll have the peace of mind that they’re not in danger.

Also, it would be a good idea if you added some caves, pots, pebbles, and driftwood.

However, it would help if you did not place so many plants and decorations that they crowd each other.

  1. Pick the Right Tankmates

Neon tetra is peaceful fish that can be stressed easily if placed with aggressive tankmates.

So, you should avoid placing them with larger fish that might see them as a meal and with nippy fish that will harass them.

Other small fish like harlequin rasboras, white cloud minnows, zebra danios are the best tankmates for neon tetras.

They school together in nature and prefer to live in groups in an aquarium, so it is best to have at least five.

  1. Allow Proper Acclimatization

If you get new neon tetras, acclimate them before adding them to the tank.

You may accomplish this by putting them in a bag with water from their old tank and then floating the bag for a quarter of an hour in their new tank. They will be able to acclimate to the temperature this way.

You may also use the drip approach to fill the bag with water from the new tank and help the tetras acclimate to the change.

Last Words

If you found your tetra swimming sideways, it requires your attention.

Keep the tank clean, add a few plants, and pick suitable tankmates to keep your fish healthy and stress-free.

Thanks for reading! We hope this article was informative and helpful.

If you have any questions or comments, please post them below.