How Many Neon Tetras In a 20 Gallon Tank (80 liters) Should You Have? - "neon tetras" by Art Poskanzer is licensed under CC BY 2.0.
How Many Neon Tetras In a 20 Gallon Tank (80 liters) Should You Have? - "neon tetras" by Art Poskanzer is licensed under CC BY 2.0.


Neon tetras are captivating and colorful freshwater fish that have captured the hearts of aquarium enthusiasts for many years. Their vibrant appearance and peaceful demeanor make them a popular choice for both beginners and experienced hobbyists. One common question that arises in the world of aquarists is how many neon tetras in a 20 gallon tank (80 liters) can thrive comfortably? In this article, we will delve into the considerations, from tank size to tank mates, and the ideal setup for a 20-gallon aquarium (80 liters) housing neon tetras.

About Neon Tetras

Neon tetras are small, vibrant freshwater fish known for their striking appearance and peaceful behavior. They are a popular choice among aquarium enthusiasts due to their beautiful colors and ease of care. Here’s a detailed description of their appearance and behavior:


  • Size: Neon tetras are tiny fish, usually reaching a maximum size of about 1 to 1.5 inches (2.5 to 3.8 cm). Their small size makes them an excellent choice for smaller aquariums.
  • Coloration: The most distinctive feature of neon tetras is their bright and captivating coloration. Their bodies are slender and elongated with a shimmering silver hue. The prominent feature is the vivid blue and red colors that runs from the nose to the base of the caudal fin, giving them their neon look.
  • Fins: Neon tetras have transparent dorsal and anal fins, which are often highlighted by a bluish iridescence. Their caudal fin, or tail fin, is forked and tends to be clear or lightly colored.
  • Eyes: Their large, round eyes are an attractive shade of silver, giving them an alert and lively appearance.


  • Social: Neon tetras are known for their social nature. They thrive in groups and should be kept in schools of at least six individuals, although larger groups are preferable. Keeping them in groups makes them feel secure and reduces stress.
  • Peaceful: Neon tetras are one of the most peaceful species of fish, making them suitable tankmates for other non-aggressive species. They are ideal for community aquariums and can coexist with other small, peaceful fish like guppies, rasboras, and corydoras.
  • Active Swimmers: These fish are active swimmers and prefer to occupy the middle and upper levels of the aquarium. They enjoy exploring the plants and swimming in open spaces.
  • Nocturnal Behavior: Neon tetras are known to exhibit some nocturnal behavior, so it’s common to see them resting or swimming more slowly during the night. Providing some low-intensity lighting during the evening can help simulate their natural habitat.
  • Feeding: Neon tetras are omnivores and readily accept a variety of foods. They have a small mouth and should be given appropriately-sized flake, pellet, or frozen foods. They particularly enjoy live or frozen brine shrimp, daphnia, and micro worms as treats.

How Many Neon Tetras In a 20 Gallon Tank (80 liters)

So, how many neon tetras in a 20 gallon tank (80 liters) should you have? The number of neon tetras you can comfortably keep in a 20-gallon tank (which is approximately 80 liters) will depend on several factors, including water quality, filtration, and the presence of other fish or tankmates. However, a general guideline is to aim for a school of at least 6 to 10 neon tetras. These fish are social and feel more secure in larger groups.

In a 20-gallon tank, you should safely be able to keep a school of 10 to 15 neon tetras, provided that your tank is adequately cycled, filtered, and maintained. It’s important to consider the following when stocking your tank:

  • Water Quality: Regular water changes and maintenance are essential to keep the water parameters stable. Neon tetras prefer slightly acidic water with a pH level around 6.5 to 7.0.
  • Filtration: A good filtration system is crucial to maintain water quality. Neon tetras are sensitive to changes in water conditions, so a stable and well-filtered environment is necessary.
  • Tank Mates: Ensure that the tank is not overstocked and choose tankmates that are peaceful and compatible with neon tetras. Avoid aggressive or larger species that might stress the neons.
  • Aquascaping: Neon tetras appreciate a well-planted aquarium with hiding spots and areas for them to swim freely. Dense vegetation and soft lighting help mimic their natural habitat.
  • Temperature: Maintain the water temperature between 72°F and 78°F (22°C to 26°C), which is suitable for neon tetras.

Remember that these are general guidelines, and you should always monitor the behavior and health of your fish. Overcrowding can lead to stress, aggression, and water quality issues, so it’s essential to strike a balance in your stocking choices. Additionally, the size and maturity of your tank will influence the number of fish it can accommodate. Regular observation and care are key to ensuring a healthy and happy environment for your neon tetras.

Tank Mates

When selecting tank mates for your neon tetras in a 20-gallon tank (80 liters), it’s crucial to choose fish and invertebrates that are peaceful, compatible in terms of water parameters and size, and won’t stress or harm your neon tetras. Here are some considerations to keep in mind:

  • Size and Aggression: Choose fish that are similar in size to neon tetras and are non-aggressive. Neon tetras are small and relatively passive, so larger or aggressive fish can stress them out or pose a risk.
  • Water Parameters: Ensure that the species you choose have similar water parameter requirements. As mentioned, neon tetras prefer slightly acidic to neutral water with a pH around 6.5 to 7.0 and a temperature of 72°F to 78°F (22°C to 26°C). Select tank mates that thrive within these conditions.
  • Temperament: Look for peaceful fish that won’t harass or outcompete neon tetras for food and space. Avoid fin-nipping species or those known for territorial behavior.
  • Schooling Fish: Consider adding other schooling or shoaling fish, as they will create a visually appealing and natural environment. Species like harlequin rasboras or glowlight tetras often make good companions.
  • Bottom-Dwellers: Including bottom-dwelling fish like corydoras catfish or small, peaceful loaches can help utilize different levels of the tank and provide variety in your aquarium.
  • Invertebrates: Some small, peaceful invertebrates like freshwater shrimp (e.g., cherry shrimp) and small snails can be suitable tank mates. They help with algae control and add interest to your tank.
  • Gouramis: Some gourami species, like honey gouramis or sparkling gouramis, are compatible with neon tetras as they are generally peaceful and prefer similar water conditions.
  • Dietary Compatibility: Ensure that the selected species have a similar diet to neon tetras. This will reduce competition for food and help ensure all inhabitants receive proper nutrition.
  • Quarantine New Fish: You may want to quarantine new fish for a few weeks before adding them to your main tank. This helps prevent the introduction of diseases that could affect your existing fish.
  • Monitoring: Regardless of your choices, it’s essential to monitor your tank and observe fish behavior regularly. If you notice any signs of aggression, stress, or health issues, be prepared to separate or rehome the problematic fish.

Keep in mind that the 20-gallon tank (80 liters) has limited space, so you’ll need to consider the individual space requirements of the chosen species. Overcrowding can lead to poor water quality and increased stress for your fish. By carefully selecting compatible tank mates and maintaining proper conditions, you can create a harmonious and thriving community aquarium for your neon tetras.

How Many Neon Tetras In a 20 Gallon Tank (80 liters) Should You Have? - "neon tetras" by Art Poskanzer is licensed under CC BY 2.0.
How Many Neon Tetras In a 20 Gallon Tank (80 liters) Should You Have? – “neon tetras” by Art Poskanzer is licensed under CC BY 2.0.

Designing Your Tank

How many neon tetras in a 20 gallon tank (80 liters) you can keep, with tank mates, also depends on how you set up your tank. Designing your aquarium for neon tetras involves creating an environment that mimics their natural habitat, providing comfort, security, and visual appeal. Here’s a step-by-step guide on how to set up your tank:

  • Substrate: Choose a dark, fine-grained substrate like sand or small gravel. Neon tetras come from dimly lit, leafy streams in South America, and a dark substrate helps to replicate their natural environment. The subdued color also makes their vibrant blue and red colors stand out.
  • Plants: Neon tetras appreciate densely planted tanks. Include a variety of live plants, such as Amazon sword, java fern, anubias, java moss, and floating plants like duckweed. These plants not only provide hiding spots but also create a sense of security and help maintain water quality. Arrange the plants in clusters and leave open spaces for swimming.
  • Hardscape: Incorporate natural-looking decorations like driftwood, rocks, and caves. These provide additional hiding spots and create a visually pleasing landscape. Be cautious with any sharp or rough decorations that might damage the delicate fins of your tetras.
  • Lighting: Use low to moderate lighting to simulate the dimly lit forest streams neon tetras are accustomed to. This also encourages the growth of live plants. You can adjust the lighting duration to about 8-10 hours per day, with a gradual increase or decrease to mimic a natural day-night cycle.
  • Filtration: Choose a suitable filter for your tank to maintain water quality. Neon tetras are sensitive to fluctuations in water parameters, so a good filter is essential to keep the water clean and stable.
  • Aeration: Neon tetras prefer slow to moderate water flow, so consider adding an air stone or adjusting the filter output to avoid strong currents.
  • Tankmates: As mentioned earlier, select peaceful, compatible tankmates that won’t stress or harass your neon tetras. Ensure there’s enough space and hiding places for all inhabitants.
  • Maintenance: Regularly trim and maintain your live plants. Vacuum the substrate during water changes to remove debris and maintain good water quality. Check your equipment to ensure it’s functioning correctly.
  • Cycling: Always cycle your tank before introducing any fish. This ensures a stable and healthy environment. Use a liquid test kit to monitor ammonia, nitrite, and nitrate levels during cycling and routine maintenance.

By carefully considering these aspects of tank design and maintenance, you can create a beautiful and suitable habitat for your neon tetras. Providing them with a well-planted, well-maintained tank will promote their well-being and showcase their stunning colors and behavior.


In conclusion, the question of how many neon tetras in a 20 gallon tank (80 liters) you can keep, can be answered with a range of 10 to 15 individuals. However, this number is not the only factor to consider when creating a suitable habitat for these charming fish. Equally important is the design and maintenance of the tank. By paying attention to the substrate, plants, water parameters, and tank mates, you can create a thriving and visually appealing environment for your neon tetras. Striking a balance between these elements ensures that your tetras can display their stunning colors and flourish in a healthy, comfortable home. So, whether you are a novice aquarist or a seasoned pro, a well-planned 20-gallon aquarium (80 liters) can provide a perfect stage for the beauty and serenity of neon tetras.