How Many Neon Tetras in a 10 gallon Tank? (2024 Guide)

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Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: June 10, 2024
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If you have a fascination for exotic South American fish, you’re in the right spot! Neon tetras are tiny beings that can add vibrant colors to your aquarium, though their small size often results in them being housed in a tank that isn’t quite large enough.

Have no fear, we’ve created a guide based on aquarium design and management experience on how many neon tetras you can fit in your fish tank along with how large neon tetras grow, and how to measure how many neon tetras per gallon.

Article Summary

  • To keep neon tetras in a 10-gallon tank, it’s recommended to have 5-6 neon tetras to provide enough space for them to swim as a school.
  • The one-inch rule (1 inch of fish per 1 gallon of water) doesn’t work well for neon tetras, as they are schooling fish that need more space to swim together.
  • For a 10-gallon tank with neon tetras, it’s suggested to start with a minimum of 10 gallons for 5 fish, or 2 gallons per 1 fish due to their active and schooling behavior.

How many neon tetras in a 10 gallon tank?

While tempting to add as many neon tetras to your 10 gallon tank as possible, it is important to consider how many neon tetras can actually fit into your aquarium.

We suggest keeping 5-6 neon tetras in a 10 gallon tank. If you believe that more neon tetra should go in a 10 gallon tank you are likely using an incorrect neon tetra size estimate. Most neon tetra grow to a maximum size of 1.5 inch at maturity, and unlike other fish there is no size difference between male and female neon tetra. They must be given enough space to swim horizontally as a school.

Neon tetras are schooling fish that tend to swim in large groups and as such need the opportunity to move together as a school. Having 5-6 neon tetra fish in a 10 gallon tank allows them ample space to swim and play in the aquarium. If you would like a larger school of neon tetra you will need a twenty gallon or thirty gallon tank for them to have enough space and exhibit their schooling behavior.

How Many Neon Tetras per Gallon?

Neon Tetras Swimming
Neon Tetras Swimming

Generally, aquarists have used the 1 inch rule to decide how many gallons of living space fish need. The 1 inch rule states for every 1 inch long the fish is at maturity you will need 1 gallon of water. This certainly wouldn’t work for other fish like an oscar fish cichlid or common pleco. Using this rule a 6 inch oscar would only need a 6 gallon tank.

Using that theory we could keep a maximum of 1 neon tetra per gallon of water. Initially, This seems like enough room for a small fish, but remember they are schooling fish you would need at least a 5 gallon tank to house them. Now imagine a school of fish trying to swim as a unit in a 5 gallon tank and there’s less room than you thought.

So how many neon tetra fish can actually fit in a 10 gallon tank? Due to tetras being active swimmers and schooling fish we recommend starting with a minimum of 10 gallons for 5 fish, or 2 gallons per 1 fish.

Is the One Inch Per Gallon Rule True?

The one inch rule is an outdated way to measure how many fish can fit in an aquarium that doesn’t take into consideration all factors when deciding tank size. While used as a general rule at pet stores and other commercial breeders it is not the best way to manage your home aquarium, and certainly does not reflect the natural environment.

The one inch rule basically says 10 neon tetras can fit in a 10 gallon tank, but when you think how many fish that are 10 inches the one inch rule says can fit in a 10 gallon tank things don’t add up. Other than size factors that should be taken into account when planning tank size includes schooling behaviors and size of school, as well as territorial and aggressive behaviors.

Using the One Inch Per Gallon Rule

For example, it’s better to keep African cichlids in a small tank rather than a bigger one because if they have free rein they’ll become aggressive. By limiting the size of the tank and therefore the swimming space you can limit aggression levels.

Another aspect of fish size that the one inch rule doesn’t take into account is that it only looks at the length of a fish, not the height. Big fish like angel fish or betta fish that have a tall tail wouldn’t do well in a tank sized to their length.

Finally, the 1-inch rule does not take into account fish waste. Fish like goldfish or common plecos are extremely messy, and often require a larger tank size or a large amount of water changes to account for this. A 10 inch common pleco would overwhelm the capabilities of the bioload of a 10 gallon tank rapidly.

How many black neon tetras in a 10 gallon tank?

Neon Tetra Tank
Neon Tetra Tank

Black neon tetras are slightly larger than neon tetras, averaging around 1.5 inches in length. But how many tetras can fit in a 10 gallon tank? Due to their slightly larger size, activity level, and the need for a school of 5 or 6 we recommend keeping them in a larger aquarium. A 20 gallon tank would be an excellent option and provide plenty of space for the active swimmers.

Be sure to have a lid on this tank, as black neon tetras are well known jumpers and will try to escape if unhappy. If you only have a 10 gallon tank available you can keep a smaller school of 3-4 neon tetras in a 10 gallon tank, be aware that this will likely mean you have to do more water changes.

How many neon tetras in a 10 gallon tank with betta?

Neon tetra fish are probably one of the only fish species that can be tank mates with betta fish. Because of their small size and speed most neon tetras will be able to dart away before bettas are able to get close enough to nip at them. Another benefit of housing neon tetras with betta is that they occupy different zones in aquariums, which works well for a small fish tank.

As to how many neon tetras you can fit into a 10 gallon tank with a betta fish you can use our recommendations from above. Adding a one female or one male betta to a 10 gallon tank where five to six neon tetras are already housed doesn’t actually increase the bioload that much and is more than manageable. Remember keeping neon tetras requires having enough tetra tank mates for a school.

In case your neon tetras or betta are messier than normal we recommend paying close attention to tank maintenance, especially for tetras in a 10 gallon tank. Regular maintenance or getting a big tank will be beneficial for both the fish.

How Many Guppies And Neon Tetras In A 10 Gallon Tank?

Though guppies are slightly larger than tetras you can comfortably house 5 fish in a 10 gallon aquarium. To solve how many tetras will fit in a 10 gallon tank with a few guppies we need to do some math. Though guppies are slightly larger than tetras you can comfortably house 5 fish in a 10 gallon aquarium.

1 guppy for every 2 gallons, and we already know that we can fit 1 neon tetra per 2 gallons. So depending whether you want a larger number of neon tetras or guppies we can assume that we could house 2 guppies and 3 tetras, 1 guppy and 4 tetras, or any variation of those.

Remember for proper tetra fish care they need to be kept in schools so having 4 guppies and 1 neon tetra fish would lead to a very unhappy community tank.

Tips For Keeping Tetras In A 5 Gallon Tank

While we recommend keeping neon tetras in a bigger tank if you’re keeping neon tetras in a small tank short term, here are our suggestions for how to keep them happy.

Water Parameters

Neon tetras are tropical, freshwater fish and their tank water should reflect that. Refer to the table below when setting up your home fish tanks.

Water Conditions
GH<10 dGH
KH1-2 dKH

Live Plants For Neon Tetras

You can place tall plants like Cryptocoryne wendtii, Ludwigia repens, or vallisneria in your neon tetra tank. Floating plants are also an option, we recommend red river floaters or dwarf water lettuce. Be aware that these fish are omnivores and many neon tetras will nibble out of your plants.

While aquatic plants do give your neon tetra tank a wide variety of areas to hide, and provide enrichment, they are not as compatible with live plants as plants are compatible with tetras. Many aquatic plants require soft, acidic water which are the water conditions neon tetra requires. At this size tank you will likely not be able to add too much plant variety, but you could add 1-2 varieties.

Aquarium Heater For Neon Tetras

As neon tetras are tropical fish it is essential to keep their temperature range from dropping below 72. If you are having trouble maintaining a higher temperature we suggest placing an aquarium heater in your tank setup.


Fish are a cold blooded species which means a fish’s body cannot regulate body temperature or make its own heat itself. Instead it reflects the temperature of the water, this is why it is necessary to have a heater in your aquarium to increase water temperature.

Filter For Neon Tetras

When keeping neon tetras in small tanks like a 5 gallon tank it is important to have a good filtration system. Not only can a good filter prevent you from having to perform water changes daily it can also remove toxic chemicals like ammonia and nitrates. Since the number of neon tetras per gallon is higher than normal it is important to keep an eye on tank conditions.

Tank Maintenance

Generally speaking, maintaining your tank should include tasks like water changes, checking on all of your fish, and monitoring your tank conditions such as pH level, temperature, and ammonia levels.

Water Change

When housing neon tetras in a small fish tank, be prepared to do water changes more often. Cleaning the tank and doing water changes regularly will help keep your tetras healthy. In a 5 gallon tank you will have to do a minimum of 2 20-30% water changes a week.

A single fish in a five gallon tank, depending on the fish’s size, would probably only need 1 water change per week. When changing fish tank water, don’t change the filter. While we can’t provide veterinary advice, this rule is pretty well vetted.

Completely changing the filter in your fish tank can lead to the removal of all the good bacteria in the system. This can lead to your aquarium cycle crashing, and your neon tetras getting ammonia or nitrate poisoning.

Feeding For Neon Tetras

Fish Food
Fish Food

Regardless of where you’re keeping your neon tetras you should be feeding them a high quality diet. In order to maintain their beautiful coloration a neon tetras diet should include a variety of flakes, produce, live food, and frozen food. Some suggestions include brine shrimp, apples, and frozen blood worms.


When feeding your fish, have a little bit of tank preservation for them and yourself. If you notice your tetras not eating all of the food go ahead and net it out then. It might save you a water change later!

Do Neon Tetras Need An Air Pump?

Depending on your tank your neon tetras might need an air pump, but they are not necessary. Wild tetras often live in blackwater streams where oxygen levels are low. However, if you are keeping fish that might need aeration like bettas, danios, or rasboras an air pump will not bother your neon tetras.


Many people like to search for free stuff for their aquariums such as air pumps and heaters. Be sure to test these items out in a fishless tank to make sure they don’t malfunction.


We hope this article has answered all of your questions regarding how many neon tetras in a 10 gallon tank. While it is tempting to have a large school of them to be able to catch large displays of their beautiful coloring, a small group of these beautiful fish can be just as attractive, especially when placed in front of the right background.

Thanks for reading! Feel free to share this with your friends in the fish keeping hobby.

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