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How Many Tetra Fish Can I Put In A 5, 10, 20 Gallons Or Liters Tank?

How Many Tetra Fish Can I Put In A 5, 10, 20 Gallons Or Liters Tank?

Just a couple of days ago a friend of mine bought a used 10-gallon aquarium on Craigslist. He had never maintained an aquarium before so he asked me for help. His main question was how many tetras he can keep in his tank while still maintaining a safe and healthy environment for the fish.

After helping him out, I figured there might be other newbie tetra keepers that might need some help with this as well. That led to me writing this article to help people like you interested in keeping tetras and other fishes that can be kept in an aquarium.

Tetras are popular aquarium fish. They are beautiful, colorful and are very easy to keep in captivity. Lemon, Black widow, and Butterfly tetras are some of the popular ones that are kept as pets.

Red-eye, Cardinal and Neon tetras are some other ones that are a good combination in a tank. You can also mix tetras with other types of fishes. Small fishes like Guppies and Danios do well with tetras. However, some tetras can be aggressive and slower fishes might get their tails and fins nipped or even killed.

It is always best to start with a school of 6 small tetras if you are new to fish keeping. Tetras are schooling fish so should be kept in numbers. If your tank is big, you can keep more fish. Smaller tanks like the 5-gallon hex tanks are more susceptible to bioload and rapid change in water chemistry.


Bioload is the waste produced by fishes. The number of fishes and the size of the fish determines the bioload produced. The more bioload requires you to change the water and clean the tank more often so do not overcrowd your fish tank. Addition of filtration and an air pump in the tank will make your cleaning job a whole lot easier when keeping tetras or any other fishes. You might also need a heater depending on your climate and the types of fishes you are going to keep.

There are lots of possible ways to maintain your tank. An inch of fish per gallon is a good way to determine how many small tetras you can keep. However, don’t forget to do your research on how big the fish will get the inch per gallon rule is not for big fishes. Fishes like Sharks, Pacu and Plecos will quickly outgrow the tanks so it is best not to keep them in your aquarium.

Local pet stores are good places to research on what species of fishes you can keep together. Ghost shrimps and snails can also be added as they produce very little bioload, eat the algae and keep the bottom of the tank clean.

Here are some good combinations of tetras, other fish, shrimps and snails that can be kept in 5, 10 or 20 gallons tank:

5 gallon/ 19 liters
5 gallon tanks are small so your choice is pretty much limited.

  • 6 neon tetras + 1 snail OR
  • 2 platys + 6 ghost shrimps OR
  • 1 beta + 6 ghost shrimps or 1 snail.

10 gallon/ 35 liters
You can put schools of 6 to 10 fish or mix it up with 2 smaller schools of different species of fish.

  • 10 lemon tetras + 6 ghost shrimps + 1 snail OR
  • 5 neon tetras and 5 guppies +1 snail OR
  • 6 ember tetra + 1 beta or 1 dwarf gourami + 10 ghost shrimps + 1 snail.

20 gallon/ 76 liters
You have more options as the tank gets bigger.

  • 1 dwarf gourami + 6 lemon tetras OR Red eye tetras + 6 Zebra danios + 1 snail OR
  • 8 lemon tetras + 8 panda cories + 1 snail + 6 ghost shrimps OR
  • 6 neon tetras + 1 beta + 6 cardinal tetras + 1 to 2 snail OR
  • 2 platys + 6 guppies + 6 panda cories + 8 ghost shrimps + 1 snail.

Whether it is a 5-gallon, 10-gallon, 20-gallon tank or even the bigger ones, providing safe and healthy environment is the key to keeping any kind of fishes including tetras. If you have any questions about aquarium keeping, don’t hesitate to ask questions in the comment section below. I would be happy to assist you.

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