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How Many Neon Tetras Can Live in a 3 Gallon Tank? (Answered)

Neon tetras are shy and easy to care for. They are considered schooling fish. Neon tetras are known for their aesthetic looks and are good for starter pets. But how many of them can live in a 3-gallon tank? Scroll down because we answered all your questions!

How many neon tetras can live in a 3-gallon tank?

The rule of thumb is that 1 inch of fish requires 1 gallon of water. Neon tetras are schooling fish. So, you can keep at most 2-3 neon tetras that are one inch long in a 3-gallon tank. You cannot keep larger neon tetras together in a 3gallon tank. Isolating Neon tetras is not recommended.

Neon tetras are most sought after because they are easy to take care of. They are beautiful in every aspect, peaceful and adaptable. Neon tetras have a bluish red hue that contrasts against a green background. 

Neon tetras are considered schooling fish. The ideal size of their school is about 5-10 neon tetras. Fish owners make a common mistake that suffocating their fish by keeping them in small tanks.

Generally, the common rule most fish owners follow is that you need a 1-gallon size for every inch of fish. Neon tetras range around the 1-inch mark. A young 1-inch neon tetra could grow up to 1.5-inch in adulthood.

So, calculating their size, a 3-gallon tank can fit 2 neon tetras at most. This excludes the space you need for essentials. So, you can not fit more than 2 neon tetras inside a 3-gallon tank.

It would be difficult for the fish as they cannot live in such a tiny place. Neon tetras move in groups, so only keeping two or three neon tetras would inhibit their growth and socialization.

Keeping fish in small containers hamper their natural growth and cause spinal deformities. It is always better to go for bigger tanks. 

Is a 3-gallon tank big enough for neon tetras?

A 3-gallon tank is not big enough for neon tetras. Fishes expect more room. Here is why –

Schooling fish:

Neon tetras are schooling fish. They tend to move and live in a group of 6-10 or even more. It is good to keep neon tetras in a group of more than five.

But this is not possible in a 3-gallon tank. You do not have enough space to accommodate more than 2 adult neon tetras in such a tiny tank.

Not enough space:

Your tank will need room for a fish filter, substrate, and air pump. That will take up space and leave less room for your neon tetras. Plus, a smaller fish tank does not mean your work gets reduced. You cannot make any mistakes while operating.

Hindrance in growth:

Neon tetras cannot move freely in a small tank. This yields to spinal deformity. In addition, your fish will show slow growth and reduced recovery symptoms. The immune system will be damaged, and your neons will have a reduced life span.

Not hardy:

Neon tetras are not hardy at all, so cycling the water will leave them vulnerable. An established big tank is best for them.

How big a tank do neon tetras need?

Young neon tetras can be 1-inch in length, and adult ones grow up to 1.5 inches. There are some 2 inches neon tetras. They do not grow more than this range.

A 1-inch neon tetra needs 1 gallon of space. So, three 2-inch neon tetras will need 3×2 gallons or 6 gallons of space. Neons like to live in groups; therefore, the larger the tank size, the better it will be for them.

A 10-gallon fish tank is good for a starter, but bigger fish tanks are preferable. But it depends on your preference and how much you would like to maintain.

How many neon tetras can you have per gallon?

Per gallon fish tanks should only comprise one inch of neon tetras. This is the general rule that experts follow. So, if you have a 5-gallon tank, you can keep five 1-inch neon tetras. But most recommend having bigger tanks.

Green neon tetras:

Green neon tetras are small in comparison. They grow up to 1.4 inches at max. You need to keep at least 8-10 green neon tetras together.

You need to make sure that your neon tetras get enough space. So, you will need a 10-gallon tank to keep your green neon tetras happy together.

Black neon tetras:

Black neon tetras are bigger than green neon tetras. They can grow up to 1.6 inches at max. It is better to keep black neon tetras in groups.

At a group of 5-6, Black neon tetras can be kept in a 10-gallon fish tank. Your black neon tetras will live in harmony, and you will get enough space for essentials and decorations.

How many neon tetras can be in a 3.5-gallon tank?

The universally accepted size of a 1-gallon fish tank is required for 1-inch of neon tetras. Neon tetras vary in size. Different species of neon tetras have different average sizes.

Some only grow up to 1.2 inches at max, while some reach 1.5 to 2 inches. Roughly speaking, you can fit 2-3 adult neon tetras at most in a 3.5-gallon tank.

This is not recommended since you need to keep space for other stuff. Neon tetras cannot live well without a good number of mates.

How many neon tetras can go in a 3-gallon tank with a betta?

Two to three neon tetras can go in a 3-gallon tank. But this is highly discouraged as this is not the standard of keeping neon tetras.

Many neon tetras owners opine that they have no problem keeping 3 neon tetras in a 3-gallon tank. You can add an invertebrate like betta to the tank. This is not recommended as the tank size will be too small for them to roam around freely.

How to keep and care for neon tetras in a 3-gallon tank?

Neon tetras are easy to keep and care for. They need low maintenance, and they do not create much fuss. Here are some tips you can follow to keep and care for neon tetras in a 3-gallon tank.

Well planted tank:

Neon tetras prefer tanks that have lots of plants. It gives them a sense of safety. Well-planted tanks give them enough place to rest and hide. 

Less cycling:

Neon tetras are not hardies, so cycling water will make them vulnerable. They may even pass out due to the disturbances.

Maintain heat:

Neon tetras are susceptible to water heat. You must install a heater for your fish to survive. The heater keeps the temperature of your tank stable.

Lower temperatures lead to certain infections, such as fin rot. You will see tails and fins missing from your fish. To keep your fish safe from fin rot, maintain a 70-81 degrees Fahrenheit temperature.

Water pH level:

Varying water pH levels will damage the skin of your neon tetras. They are best kept at a range of 6.0-7.0 pH value.

Getting too acidic or alkaline will cause skin infections. Maintain the pH range using reverse osmosis (RO) at all costs.


Neon tetras are shy and peaceful and take time to adapt to their surroundings. So, do not expect them to be exploring all your corners on the first day.

Have patience and feed them 2-3 times every day, and they will start to show their true colors.

Final thoughts

A 3-gallon tank will not cut it for a school of 8-10 neon tetras. So, many recommended getting larger fish tanks as neon tetras prefer more space and buddies. They are easy to care for, but you need some initial commitments. Feed them and keep water parameters stable.