Why do my Neon Tetras Stay at the Bottom of the Tank?

Quite often, I caught my neon tetras staying at the bottom of the tank. As time passed, I learned that it indicates that something went wrong. After a few attempts and extensive research, I found why this happens and how to deal with the issue.

Neon tetras tend to stay at the bottom of the tank when stressed, primarily due to aggressive tankmates and inappropriate water conditions, including pH and temperature. However, tetras also sit at the bottom of the tank when carrying a disease, such as Ich, infections, and swim bladder disorders.

As we proceed, I will show you how to treat the underlying conditions forcing your tetras to stay at the bottom. That includes using products to test the water pH and chemistry, such as the API Aquarium Test Kit (link to Amazon).

Why do my Tetras Stay at The Bottom of The Tank?

Different types of tetras prefer different sections of the aquarium. Black neons, for instance, prefer the upper half of the tank. Cardinals, on the other hand, prefer the lower half. They wouldn’t be out of place at the bottom. However, this doesn’t apply to ordinary neon tetras. 

Obviously, you cannot always predict their personalities. Some neon tetras are naturally drawn to the lower half of the aquarium. But the majority of neon tetras do not share this trait, which is why many aquarists show concern when their neon tetras begin to frequent the bottom.

Common causes of this behavior vary, ranging from benign to potentially fatal factors, including:

1. The Tetras Have Not Acclimatized Properly

Did you acclimate your neon tetras to their new tank? That’s a valid question since the transition to a new tank can traumatize fish. Acclimation processes are supposed to alleviate the stress associated with such transitions by giving the fish in question an opportunity to grow accustomed to the conditions they will encounter in their new environment before adding them to the tank.

But some fish will manifest signs of shock and stress even when you have adequately acclimated them. Their shy personalities will drive them to the bottom or into hiding until they grow accustomed to their surroundings. 

Some neon tetras will remain active during this period. Others will become listless and Lethargic. They may even lie still at the bottom. Yet, if the transition is the only factor causing the issue, your tetras’ behavior is likely to change over time.

2. Your Tetras Live With Aggressive Tankmates

Consider the other fish in your tank. Naturally, aggressive neighbors are more likely to send neon tetras to the bottom or into hiding. Most aquarists know this. If the aggressive fish prefer the aquarium’s middle or upper sections, the tetras will flee to the bottom, where they are less likely to encounter their bullies.

But that isn’t your only concern. Neon tetras that are living in comfortable aquatic environments have laid-back personalities. If their neighbors are very active fish (such as danios), the neon tetras may take refuge at the bottom because that is the only place where they can find rest.

3. Your Tetras Are Stressed

Stress can drive neon tetras to the bottom. And unfortunately for you, aquariums can be assaulted by any one of a dozen or more sources of stress. That includes aggressive tankmates, hyperactive fish, and transitions to new environments.

It can also include poor water conditions such as the wrong pH and hardness and excessively bright lighting, to mention but a few. Look for other signs before you conclude that your fish is frequenting the bottom because of stress.

Stressed fish will lose their appetite. They will become inactive or violent, and their colors are also just as likely to fade. Suppose your neon tetras have manifested these signs and more, but you haven’t identified any symptoms of illnesses and infections. In that case, you can assume that stress is responsible for their behavior.

4. Inappropriate Cycling

If your tank wasn’t correctly cycled, the extreme conditions in the aquarium would cause significant distress among your fish. The neon tetras may respond by running to and staying at the bottom. Cycling can take anywhere between four and six weeks.

If the ammonia and nitrite concentrations keep spiking despite your best efforts, your tank isn’t properly cycled. The absence of proper cycling might even kill your neon tetras in the long run. Their penchant for staying at the bottom in such situations is the least of your concerns.

5. There Are Too Few Tetras

Neon tetras are schooling fish, which is why you should keep them in groups. Neon tetras that are living alone or in small groups don’t feel secure. Their loneliness and anxiety will compel them to behave in unusual ways. That includes swimming and staying at the bottom.

6. Your Tetras Are Sick

Sick neon tetras are more likely to sink to the bottom than their healthy counterparts.[1] The reasons vary depending on the disease. For instance, if they have swim bladder disease, the ailment may compromise their ability to swim, preventing them from leaving the lower half of the tank. Swim bladder disease can even stop neon tetras from escaping the substrate.

With a disease like ich, the fish may frequent the bottom because they want to scratch against the substrate. Ich produces an itching sensation that fish can alleviate, albeit temporarily, by scratching against objects in the tank. If your neon tetras have ich, they may frequent the bottom because it allows them to scratch their bodies against the gravel.

You also have bacterial and parasitic infections that rob neon tetras of their strength. In other words, they have no choice but to sink to the bottom because they are too weak and tired to swim in the upper sections. It is easier for them to descend to the substrate.

7. Inadequate Temperature

If your tank is too hot, your neon tetras have every reason to run to the bottom since the water at the bottom is cooler. Because hot water cannot hold as much oxygen as its colder counterpart, any oxygen deficiencies that manifest as a result of the elevated temperatures will also encourage the fish to stay at the bottom, where the water is not only cooler but more oxygenated.

How to Treat Neon Tetras That Stay at The Bottom?

You shouldn’t ignore a neon tetra that has chosen to stay at the bottom. If the condition responsible for its behavior is serious, it could die. This is why you are encouraged to take the following steps:

1. Conduct a Water Change

Start by performing a water change. This lowers the toxins in the water while also removing any agents that are responsible for the diseases and infections assaulting your neon tetras. A water change will also remove debris and pollutants that may hinder the recovery of your fish.

Bear in mind that the water replacement should be gradual. If you own a relatively large tank (20 gallons and more), replace 30-40% percent of the water weekly. Tanks containing less than 20 gallons should be treated more gently. Replace 15-20 percent each week in those.

2. Adjust the Water for Neon Tetras

Your neon tetra’s aquatic environment should be suitable for that type of fish. You have to keep the following in mind:

  • Water pH – The pH should sit somewhere between 5.5 and 6.8.[2] You should test the water’s pH regularly, mainly when you perform a water change. That is where I typically recommend getting the API Aquarium Test Kit (link to Amazon). That bundle will accurately measure your pH, ammonia, nitrates, and nitrites levels.
  • Temperature – The temperature should range between 70 and 80 degrees F for neon tetras. However, the temperature should also be stable and feature no fluctuations. The only device I found helpful on this matter is the Cobalt Aquatics Flat Neo-Therm Heater (link to Amazon), which I also reviewed here.
  • Tank Size – Neon tetras are small fish. They have an average size of 1.5 inches. However, they still require a minimum of ten gallons of water because you have to keep them in groups. On that matter, feel free to check the aquarium that I use.
  • Cycling – Don’t add neon tetras to a tank unless it is fully cycled. As was noted before, cycling can take four to six weeks to complete. Without proper cycling, your aquarium will struggle and ultimately fail to overcome high ammonia and nitrite levels that will kill your neon tetras.
  • Filter – The tank requires a filter to keep the water clean. The filter’s intake should be covered to prevent the neon tetras from being sucked in. As you now know, the fish are tiny. I personally use the MarineLand Penguin (link to Amazon).

3. Pick the Right Tankmates

Neon tetras should be kept in groups of at least six. This company will make them feel secure. Because they are friendly fish, they can share their tank with other species. However, it would help if you looked for peaceful fish that are less likely to attack the neon tetras. 

That includes guppies, mollies, and cardinal tetras.[3] Remove any fish whose aggressive actions against the neon tetras have persisted despite your best efforts. The neon tetras will stay at the bottom until they feel safe.

4. Feed Your Tetras Properly

Neon tetras cannot recover unless you feed them to their satisfaction. The creatures are omnivores that eat everything from freeze-dried brine shrimp and bloodworms to fruit flies and frozen peas. It would be best if you fed them no more than three times a day.

To make sure the meal portions are equal and served in time, I highly suggest considering an automatic feeder. In my tank, I use the Eheim Automatic Feeding Unit (link to Amazon). That device allows me to forget anything related to my fish’s feeding schedule. 

5. Introduce a Few Plants

Your tank should be heavily planted. Add plants and objects like pots and driftwood in sufficient quantities.[4] They provide shade and privacy. The neon tetras use them to stay hidden from predators. Their presence allows the creatures to feel more secure. This encourages the neon tetras to swim freely throughout the tank.

6. Provide Enough Oxygen

If you have an oxygen deficiency and the filter’s agitation has failed to solve it, add some powerheads and spray bar aerators.[5] They will increase the rate at which oxygen enters the tank. The powerheads can also ensure that oxygen is evenly distributed. This will prevent oxygen-deficient pockets from forming.

You can also use air stones. The one that does a fantastic job in my tank is the Hygger Aquarium Air Stone Kit (link to Amazon). All you have to do is to place the device in the middle of your tank. The air stone will take care of the rest.

7. Treat Potential Diseases

Your approach to diseases will depend on the illness your neon tetras have contracted. For instance, you can combat ich by raising the temperature to 86 degrees F and keeping it at this point for three days. You can also treat the fish with products like Cupramine, not to mention treating the tank with aquarium salt.

Swim bladder disease will respond just as positively to an elevation in temperature. Though, in this case, you are also expected to keep the neon tetras on a fast (if they have digestive issues) before feeding them cooked and peeled peas.[6]

If they have dropsy, you should euthanize them because they can’t be cured.[7] Try to match the solution to the disease. If you don’t know how to proceed, quarantine the sick neon tetras while you consult a vet. This will prevent the sick fish from infecting their neighbors. You should quarantine the fish even when you haven’t yet identified the disease ailing them. It is always better to apply caution in such situations.

8. Acclimatize New Fish

New neon tetras are susceptible to shock. Besides acclimating them, you can ease their transition by creating a peaceful and welcoming environment in the tank. The water should have the right parameters, so try to test it beforehand. If you have aggressive fish in the tank, add a divider. 

This will give the new tetras a chance to grow comfortable with their new environment before they are forced to confront their hostile neighbors. If you have a particularly timid neon tetra, keep it in a breeding box. This allows the creature to live in the tank without interacting with its inhabitants. Over time, it will grow accustomed to its new surroundings.

If you found this article useful, these may also interest you:


Tetras that choose to frequent the lower sections of the tank should draw your attention. That usually indicates that something is stressing your fish. The first step would be testing the water pH, nitrates, nitrites, and ammonia.

Those are the byproducts of fish’ waste, and they tend to accumulate over time. If your water is okay, make sure that your tetras don’t swim next to aggressive tankmates. You should also check if your tetras are sluggish and show no interest in food. In this case, your fish might be sick and should be in quarantine.


  1. https://lakedistrict-coastaquarium.co.uk/everything-you-need-to-know-about-a-sick-neon-tetra/
  2. https://www.wikihow.com/Care-for-Neon-Tetra
  3. https://www.tropicalfishcareguides.com/aquarium-fish/neon-tetra-tank-mates/
  4. https://www.fishkeepingworld.com/neon-tetra/
  5. https://www.aquariumnexus.com/neon-tetras-oxygen-air-pump/
  6. https://www.cuteness.com/article/cure-bladder-disease-molly-fish
  7. https://www.thesprucepets.com/dropsy-in-aquarium-fish-1381806

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