How Many Neon Tetra In 20-Gallon Tank?

Neon Tetra In 20-Gallon Tank

It isn’t a new thing to fall in love with neon tetras when you see them for the first time. Their vibrant color and active nature catch the attention of anyone who loves being close to nature. And thank god for the hardy nature of these neon tetras, this fish will ideal for you even if you are just starting fish keeping. But how many neon tetra in a 20-gallon tank?

When you are talking about a 20-gallon tank, you need to consider the size of your neon tetra fish. According to the rule of thumb, you can keep 10 to 13 neon tetras in the 20-gallon tank depending on your preference and experience.

If you planning to keep more than 6 neon tetras in the tank, then start with the 20-gallon tank. It will be ideal for small schooling yet actively swimming fish like neon tetras.

As you might have heard about the one-inch one-gallon rule in fish keeping, we will be using the same rule to determine the number of neon tetras you can keep in the tank.

These little pieces of information won’t make it easy for you to keep neon tetras, will they?

So, let’s get into detail and know, how, why, and what number is accurate for neon tetra in 20-gallons accommodation.

About Neon Tetras: A Quick Overview

Neon tetras are known for their glaring colors and energetic behavior. They belong to the Characidae family and only live-in freshwater. This breed of fish is very popular with tank owners.

Here is a quick revision about neon tetras to make it smoother to move ahead in our journey.

Care Level Easy, Beginner
Temperament Peaceful, Schooling
Lifespan 5 to 10 Years
Size 1.5 inches
Diet Omnivorous
Minimum Tank Size 10 Gallons
Tank Set-Up Freshwater, Well-Planted
Temperature 70 to 82°F
pH 6 to 7
Hardness 2 to 10 dH

How Many Neon Tetra In 20-Gallon Tank?

So many questions linger back in your head when you plan to acquire an aquarium. And when you get beautiful schooling fish like neon tetras to keep in the tank, the questions pile up making it hard for you to make any decision.

I know the feeling of being lost and confused about fish keeping, especially with neon tetras.

When I first acquired neon tetras for my 20-gallon tank, I had so many questions and confusion around me.

So, let me help you get over the dilemma and confusion and make your fish keeping hobby a little easier.

How Many Neon tetra Fish Per Gallon Of Water?

Do you know about the one-inch one-gallon rule about fishkeeping? For each inch of fish, you need to add one gallon of water to the aquarium.

This rule only applies to small fish that are less than 3 inches in size. Also, keep in mind that the rule doesn’t always work on bigger fish such as Oscars or Goldfish.

So you can keep 1 neon tetra fish in 2 gallon of water, although this is not actually ideal for you to keep 1 neon tetra only.

How Many Neon Tetra In 20-Gallon Tank?

So, following this rule we will decide how many neon tetras to keep in a 20-gallon tank. Firstly, a neon tetra can reach the maximum size of about 2 inches.

In general, the usual length of a neon tetra is 1.75 inches. But let us estimate the size of neon tetras in a whole number for a 20-gallons tank.

So, by our calculation, if we estimate that a neon tetra can grow up to 2inches, a 20-gallon tank will be able to keep 20/2 which is 10 tetras.

Thus, if we go by their real size rather than the estimation, we will be able to fit 20/1.75 i.e., 11.42 neon tetras in the tank.

Rounding up you can go for 12 neon tetras in the 20-gallon tank with no issues or fear of overcrowding the tank.

To be honest, you will still have a lot of spare room in the tank. And hey, I talk from experience, you can easily keep about 13 neon tetras in 20 Gallon tank. 

And, when you will be experienced enough in fish keeping, you can easily keep nearly 24 neon tetras in a 20-gallon tank.

Since they are schooling fish and swim horizontally most of the time, they will stick with each other without taking up all the space and making the aquarium crowded.

Although if you decide to go with 20 neon tetras in a 20-gallon tank, make sure you’re using a good filter and keep the tank clean and hygienic.

What Tank Size Does Neon Tetra Need?

The ideal size of the tank depends upon the number of neon tetra you’re planning to keep.

An average size would be 20 gallons tank but you can have 10 gallons of the tank if you’re planning to keep only a few of them.

If you go according to the ideal school size for neon tetras, it is okay to go for a 10-gallon tank. But it is wise to keep 15 neon tetras in a 20-gallon tank.

This will give them enough space to swim around the tank and making them happy and healthy.

Why Do Neon Tetras Need To Be In Groups?

Neon tetras are schooling fish and thrive in the tank when they are kept with their own. Let me share a personal experience with you.

Once, I tried to keep a neon tetra in a tank alone as I was new at fish keeping and had no idea about loneliness in fish. (I know it now, what a blunder I did back then.)

My neon tetra was fine for few days but after a while, it started to act sluggish, quit eating food I gave, and barely even swim.

I got worried, checked the water parameters time and again, and even try to adjust the heater and equipment again.

But nothing made any difference and my neon tetra got sicker and more passive. After few days, it died and I found it floating in the tank.

This broke my heart as I was very new at fish keeping and lost the very first fish. So, you see, loneliness is a real thing in fish as well and their mental health plays an important role in deciding their peaceful and happy life.

When kept alone, neon tetras get stressed and scared. After a while they will stop eating and hence, due to starvation and malnutrition, these tetras become susceptible to diseases.

Weak and sad fish will not live long and you will find your neon tetra floating in the tank dead if you keep them alone for long period.

What Happens If I Overcrowd My 20-Gallon Neon Tetra Tank?

Let me ask you something, how would you feel if you are trapped in a small room with 40 other people and have no way out?

I don’t think anyone will be able to survive in a confined space where there is no place to move towards.

The same happens to neon tetras when you keep more than 24 neon tetras in a 20-gallon tank. Do not push the limit, it will only change into your worst nightmare.

The excretion from neon tetras will accumulate a high level of ammonia in the tank. Even the beneficial bacteria present in the tank will not be able to perform the aquarium nitrogen cycle.

These bacteria will not be able to convert all the ammonia and nitrite into nitrate. Work overload will kill these helpful bacteria as well.

Pollution, unclear and foamy water, and aquarium Ammonia poisoning will be fatal for your neon tetras.

Your tetras will be stressed, gasping, and trying their best to find a space to breathe or even swim.

Stress can weaken the immunity system of neon tetras along with the peaking of pollution bringing disease-causing agents in the tank.

You are pushing your neon tetras towards their death when you keep more fish in the aquarium than recommended.

Aquarium Needs Neon Tetra

Originally from the warm rivers of South America including the countries, Brazil, Peru, and Colombia, these tetras can be found in the Amazon river.

There are lots of vegetation and fallen leaves. You will find them living in groups and spend most of their time in the middle of the water column.

Water Temperature For Neon Tetra In 20-Gallons Tank

For an ideal water condition, the temperature of the tank must be properly maintained. The temperature must be kept between 70 to 81 degrees Fahrenheit.

Neon tetras will need heater for survival in the captivity. Eheim Jager aquarium heater will be one of the ideal choice for neon tetra 20-gallon tank.

Learn more about Maximum Water Temperature For Neon Tetras and  Minimum Water Temperature For Neon Tetras.

Filtration For Neon Tetra In 20-Gallon Tank

These fish are very sensitive to water changes and must require optimal water to survive. Tetras require a matured tank that is well established and used for a certain period.

If you don’t manage to keep the newly cycled water like the tetras are used to then it might result in a serious consequence or even death.

In order to do so, you can go for Tetra Whisper Internal Filter which has a built-in air pump as well.

You need to test the water time and often to keep the ammonia and nitrite level in check. API Master Freshwater Test Kit will help you test the water easily at home.

To mature the tank quickly to keep neon tetras, you can choose to use API Quick Start Nitrifying Bacteria. This will boost the nitrogen cycle in the aquarium.

I have also written an article on Do Neon Tetras Need Filter To Survive?

Lighting For Neon Tetra In 20 Gallon Tank

As per the lights, they require a low watt fluorescent light and the watt that should be provided is 2 watts per gallon.

NICREW ClassicLED Aquarium Light is an ideal choice for light when it comes to neon tetra tank. You can fid it easily on

But remember to turn off the light according to the sunrise and sunset schedule. It is not wise to leave the light on for all day and night.

12 to 14 hours of lighting in the tank is sufficient for neon tetras. Any more than that can bring consequences you won’t like.

pH And Hardness In 20-Gallon Neon Tetra Tank

Neon tetras are hardy fish and can adjust in a huge range of water pH and temperature. But the fluctuation in water pH level does affect neon tetras.

Moreover, the pH level should be kept below 7.0 and above 6.0, Also, try to maintain soft water that is <10DGH.

API Master Freshwater Test Kit will come in handy when it comes to testing the pH and hardness of aquarium water.

Decorations And Substrate For Neon Tetra In 20 Gallon Tank

While keeping them in an aquarium, you should always keep in mind how they are living in their natural habitat and should imitate the habitat for the best results.

In the tank, there should be heavily planted plants. Also, make sure to create a dark environment for them.

ADA Aquasoil Amazonia is the best substrate for neon tetra and its color mimics their natural habitat too.

I have also written an article on Best Aquarium Substrate For Neon Tetra. Take a look!!!

You can keep plants like Java Moss, Java Fern, Amazon Sword, etc. in the tank for your neon tetras.

You might like to read more about 10 Best Aquarium Plants For Tetra Fish.

Neon Tetra Tankmates In 20-Gallon Tank

Generally, neon tetras are non-aggressive and peaceful fish so they can be the perfect community fish.

However, you should keep in mind the larger fish because they can eat them. So, small fish are perfect tank mates for them. The ideal list of fish that suits neon tetra can be:

  • Barbs
  • Cory Catfish
  • Dwarf Cichlids
  • Gouramis

The fishes that should be avoided are big Gouramis such as the Pearl, and Opaline. This is because they can eat the neon tetra as it is small in size. Other fish includes Bettas, Angelfish, and Cichlids.

Neon Tetra Feeding and Diet

Neon tetras are mostly omnivorous in their natural environment, they eat both meat and plants.

If you observe it closely, you can find neon tetras eating algae around the tank. Additionally, you can feed neon tetras larvae of mosquitoes, and even insects.

They don’t need a specific food item and will enjoy eating different types of food that can include flakes, pellets, or even live.

They prefer high-quality pellets to match the requirement of their diet. You can find such quality pellets in blood worms, brine shrimp, tubifex, and daphnia.

These are all the nonveg items but if you go into natural feeding you can leave them to eat the larvae and the algae. Learn more about Do Neon Tetras Eat Algae As Their Food? How Do I Prepare Algae Wafers?

One thing to consider is that when feeding worms or shrimps make sure to only feed them small ones else, they might have problems swallowing them.

Frequently Asked Questions (FAQs)

Here are answers to few questions that you might be thinking about as well. Hope this helps.

Do Neon Tetras Eat Dead Fish?

If a fish dies, yes, neon tetras can eat dead fish. It’s like normal food to them and will consume them if they are hungry.

These tetras will eat anything that will fit in their mouth. And dead and rotting fish will be a perfect diet for them.

Do Neon Tetras Die Easily?

Neon tetras can live up to ten years if properly maintained, but they can easily die if the tank environment is not suitable for them.

The drastic change in water chemistry adversely affects neon tetras. Neon tetras might be hardy but constant fluctuation will affect them to death.

Do Neon Tetras Need Light At Night?

Generally speaking, no. They don’t need light at night because they need 12-14 hours of light to maintain the right circadian rhythm which they usually get during the day.

So, you see it is quite unnecessary to turn on the night during night, actually it is worse. More exposure to light can discolor the vibrant and beautiful neon tetras.

How Many Neon Tetras Can I put In A 3 Gallon Tank?

By applying the rule, you can put around 4 to 5 small neon tetras in a 3-gallon tank. However, you can increase the number up to 7 or 8.

But it is wise to switch to 10-gallon tank as it is the ideal minimum tank size for neon tetras.


In conclusion, neon tetras are wonderful and one of the best fish you can keep in the aquarium as a beginner. And, the number of them won’t matter as long as it is larger than 6. The ideal school size of neon tetras plays an important role when it comes to keeping them in captivity. You should never keep neon tetra alone in the tank and when it comes to a 20-gallon tank, keep at least 10 of them together.

Just follow the instructions I gave you and you will be a good fish keeper in no time. Furthermore, if you have any queries or questions about them, drop them in the comment section.

Good Luck!!!

Happy Fishkeeping!!!

Recommended Articles:

  1. How Many Neon Tetras in a 10-Gallon Tank?
  2. Why Is My Neon Tetra Not Eating? – Here Is What You Can Do
  3. How Many Neon Tetras In A 1-Gallon Tank?
  4. How Many Neon Tetras In A 2.5-Gallon Tank?

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