How Big Do Neon Tetras Get? (And How To Increase Size)

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Last Updated on 2023-05-24

Neon Tetras are amazing fish. They are colorful, fun to watch, active, and super easy to care for. It’s easy to see why these fish are so popular for pets. When you add a new fish to your aquarium, such as a Neon Tetra, you want to do some research, so you know how big they are going to be.

If you get a fish that isn’t the size you are expecting, it can quickly outgrow the tank they are living in. Luckily when it comes to Neon Tetras, they aren’t very big. That means they aren’t likely to grow out of your current tank.

This breed of fish thrives when living as a school, so it is going to make a Neon Tetra happiest to have a minimum of ten in one tank. This will be easy because they are pretty small. They aren’t the smallest fish ever, but you do not need to worry about them outgrowing a tank.

How Big Do Neon Tetras Get?

Neon Tetras usually grow to be an average of 1.2 inches or 3 centimeters long. They have the ability to grow as long as 2.5 inches long, but it is not as common. There is also a size difference between female and male Neon Tetras.

It is extremely common for females to be larger than males. The females will also have a slightly rounded belly, while males will just have flat bellies. Even though the females are larger than males, you can expect the males to have larger fins. The size of the fish is often how you can tell whether the fish is a male or female.

When Do Neon Tetras Reach Their Maximum Size?

The average Neon Tetra will grow to its maximum size within the first year of its life. In most cases, they will be fully grown by the time they reach nine months of age. Every fish is different, so it could take them less or more time to grow completely.

How Fast Do Neon Tetras Grow?

When it comes to knowing how fast your Neon Tetras grow, it will benefit you when deciding if your current tank is large enough for the entire school of fish. This information can help you be prepared should you need to upgrade tanks sooner than expected.

The fish are not known to grow very quickly. It can take as long as two months for your Neon Tetra to even reach 1/4 inch in length. When you have multiple Neon Tetra in one tank, you might want a larger tank, so they aren’t swimming into each other all the time.

How Can You Help Neon Tetras Reach Their Full Size?

There are a few different things you can do to help your Neon Tetras reach their full size. It is not recommended to try to speed up their growth, as this can significantly reduce their life expectancy, and they won’t live as long.

Water Quality

The quality of the water you keep your Neon Tetras in can help their growth. You need to provide these fish with proper parameters to significantly help them grow. These fish are tropical, so they require a water temperature of around 81 degrees Fahrenheit.

Providing Neon Tetra with plants in their tank can help keep their stress level under control. Reducing their stress level will make them happier and help their growth. Without places to hide, the fish would get too stressed out and might not survive long enough to grow to their full size.

To ensure the water in the tank is always perfect, it will be beneficial to you and the fish to invest in quality equipment like filters, heaters, and lighting. Neon Tetras enjoy light, but not too much.

Food Quality

Neon Tetras are going to need high-quality food that contains all of the necessary nutrients to keep them healthy. Eating the proper food can ensure that the fish will grow and become a strong adult fish. The best foods to feed for the best growth are going to be high protein with all the minerals and vitamins they need.

While it is important to make sure they eat the proper foods to grow, you need to make sure you don’t feed them too much. If they eat too much, they can gain unhealthy weight. This won’t help your fish grow faster, and it can even be harmful to their health in the near future.

Tank Size

The size of the tank can actually impact how the Neon Tetra grows. If you don’t think your Neon Tetra is developing how it should be, you can put them into a larger tank. However, if the tank is too large with other fish in it, the Tetra might not be able to get to food if they are too small.

If you feel they aren’t getting any better, you should only move the Neon Tetra to a larger tank. They should preferably only be put in a larger tank if they are going to be the only fish in there. When they have to fight for food, they can quickly become malnourished, which will not help their growth.

This doesn’t mean they can’t have tank mates. It is just recommended to wait until they reach their full growth before putting them in a tank with other fish mates. This will ensure that they don’t have to fight for food, and they can grow with access to proper nutrition.

Separate Males and Females

Neon Tetras are physically ready to have babies when they are twelve weeks old. If you have males and females in the same tank, it is likely they will reproduce. If a female fish becomes pregnant too young, their energy will be used for growing the babies instead of themselves.

Keep males and females in different takes until they reach their full growth size. This will allow the female Neon Tetras to focus on their own growth instead of growing babies and keeping them healthier.

There are a few different ways you can determine if the Neon Tetra is male or female to ensure they are properly separated. The females are going to be larger with a slightly rounded belly. The males will be smaller with a flat belly.

You will also take notice of the stripe on their body. This stripe is blue and will differ between male and female Neon Tetras. The female will have a slightly curved stripe on her body. Males will have a very straight stripe.

What Can Hinder a Neon Tetras Growth?

Just like the listed ways above to help your Neon Tetra grow, the opposite can cause issues for the growth of your Neon Tetra. Fish can have growth issues if they are not properly taken care of and their tank isn’t kept properly.

If the fish tank doesn’t have the right water temperature or the fish aren’t eating the highest quality food, this can cause issues with their growth. Always be careful to make sure you are feeding your fish the right food.

Improper Water Quality

The quality of the water your Neon Tetras are kept in is extremely important. If the water isn’t just right, they can quickly become unhappy and stressed. If the fish are unhappy and stressed, they won’t grow like they are supposed to. This could slow down the process of growing or halt it completely.

You need to make sure the tank is always at the right temperature with the right chemical balance. Your fish will also need to have plants in the tank with them that will also help with the quality of the water. If your Neon Tetra isn’t growing, the first thing you should check is the water conditions.

Improper Nutrition

Another reason Neon Tetras might not grow is that they aren’t getting the right nutrition. This could be that you aren’t feeding them the right food. These fish need food that has high protein along with minerals and vitamins to keep them healthy.

If they aren’t getting fed quality food, they aren’t likely to flourish in growth. The issue could also be overfeeding the fish. It is recommended to always watch your fish when you feed them to make sure they are eating properly. You should only feed them food they can finish in two minutes. Any more can cause the fish to become sick and cause other issues.

Tank is Too Small

While Neon Tetras themselves aren’t very large and are unlikely to outgrow a tank, they could be unhappy in a tank that is too small. Since Neon Tetras are schooling fish, they like to be around other Neon Tetra. That said, it is highly recommended to have a tank that has 2 gallons of water for each fish.

When the tank is too small, the fish will quickly feel cramped. This will make them feel stressed and uncomfortable. When a Neon Tetra is stressed, they are way less likely to grow at a proper rate. If the stress isn’t addressed, the fish can suffer consequences.

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Tank is Too Big

There is also a possibility that the tank your Neon Tetra lives in is too big. This will be most common if there are other fish in the tank with the Neon Tetra. The issue with having a tank that is too large is that the smaller fish aren’t likely going to get to the food before the other fish do.

When the Neon Tetra isn’t able to get proper nutrition because they are fighting for it against larger fish, they won’t grow properly. Even if they are in a large tank with just Neon Tetra, there is still the chance that at least one fish won’t be able to make it to the food before it is all gone.

If you notice a fish is much smaller than the rest, you might want to downsize. This should help the problem. While that fish might not catch up in size, it will have the ability to be properly nourished in a more appropriate size tank.


As stated above, Neon Tetras can start breeding as early as twelve weeks of age, but they aren’t fully grown until about nine months. If a female Neon Tetra becomes pregnant, the energy she would have used to grow herself will have to be used to grow babies.

During this process, the growth of the female Neon Tetra will be put on hold. This can mean she will find behind in size compared to the other fish in the tank. To prevent this, you need to keep male and female fish separate until they are at least nine months and fully grown.


When you are considering adding new fish to your tank, it is extremely important to know exactly how big they will get. It will prevent you from being blindsided and needing to buy a whole new tank that you weren’t expecting. Luckily, Neon Tetras aren’t likely to outgrow a tank that they are kept in, but they do need one of proper size.

Neon Tetras only grow to be, on average, 1.2 inches long. In some cases, they can even grow to 2.5 inches long. While this is rare, it does happen. The fish will become fully grown by the time they are nine months old.

Even though the fish aren’t very big, they are school fish. The size of the school will help you decide how big your tank needs to be. It is highly recommended that your tank can hold 2 gallons of water per fish in the tank. If you have a school of 10 Neon Tetras, you will need a 20-gallon tank.

To help your Neon Tetra grow efficiently, you will want to make sure they are eating a proper diet, have optimal water conditions, have a proper tank size, and males and females should be kept separate. While these can help the Neon Tetra grow, the opposite can easily hinder their growth.

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