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 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 safe and healthy environment for the fishes.

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 is 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 bio load and rapid change in water chemistry.


Bio load is the waste produced by fishes. The number of fishes and the size of the fishes determine the bio load produced. The more bio load requires you to change the water and clean the tank more often so do not over crowd 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 as 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 bio load, eat the algae and keep the bottom of the tank clean.

Here are some good combinations of tetras, other fishes, 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 fishes 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 in 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.

Please feel free to comment down below and share your thoughts. Plus, if you like this pet article Tweet it, share it in Facebook or your favorite social media outlets.

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

  1. Hi! I have an Aqueon 20 gallon long tank (30x12x13) planted with dwarf hair grass . I wanted to keep only Ember Tetras and was thinking of getting about 20 (and possibly 2 or 3 ghost shrimp). Would this be too much bio load? Thank you!

    • Hi Andres,
      I think 20 Ember Tetras would be little too many, even though they are peaceful schooling fish and you have a 20-gallon tank. If you are going to keep 2 or 3 ghost shrimps, I think you should go for no more than about 15 Embers.

      You mentioned you have dwarf hair grass. Taller plants should also be provided since they love swimming around the middle of the tank. They also thrive if you have caves, rocks, and driftwood.

      • Thank you! I have a 24” piece of driftwood that stretches across the tank, the tetras will have plenty of hiding spots. Thank you for you help!

        • My pleasure. Keep us updated on how it goes. You can even send us a picture using the contact us tab if you want, so we can post it in our Instagram page. Thanks

  2. Hi, I have a tank that’s roughly 12 or 12 litres, and bought 2 small cherry shrimp, 2 cherry barbs, and 2 small blacktail/fin tetra. The aquarium owner told me I can get 4 more cardinal/neon tetras when they come in next week, but I’m worried it will be too much. Any suggestions?

    • Hey there,
      I know cherry shrimp and cherry barbs are not too big but your tank is only 12 liters. Do you mean black skirt tetras when you mentioned blacktail/fin tetras? Black skirt tetras are known to be semi-aggressive and would not be compatible with cardinal/neon tetras in such a small tank. If you get a bigger tank, you could put them together as there would be plenty of space for both varieties.

  3. I have a 5 gallon tank with 2 adf and 2 snails… many tetras can I add?

    • African Dwarf Frogs (ADFs) are docile and don’t bother any other tank mates. The main problem in keeping fish together with ADFs is that the fish might consume all the food before frogs can get to it.

      Now once you get over the feeding issue, if you do decide to keep tetras in the same tank, I suggest you keep only 3-4 of them considering the fact that your tank is only 5 gallons and you already have 2 ADFs and 2 snails.

      Personally, I strongly suggest keeping ADFs by themselves as they thrive better that way. I don’t think snails are going to bother them. Its just that when fish is added to the tank, they tend to hide more and not flourish as good.

      I hope that helps. Let us know what you decide. Thank you and have a great one.

  4. I have 10 glofish and 7 neon danios in a 37 gallon tank 2 of my danios dont seem to be growing is my tank of crowed
    And will they reproduce on their own or do they need special care for that

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