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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.

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

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

  1. I have a 20 gallon tank and I have 4 Black Skirt Tetra, 2 Gold Skirt Tetra and 3 Zebra Danio but I want to get 3more Zebra Danio will that be too many

  2. Hi I recently got a 21 litre fish tank (around 5 gallons) and am not sure how many fish I can put in I was thinking about maybe getting rummy nose tetras and a snail but am not sure how many tetras I would be able to put in and since you said you should have 6 of them I’m a bit stuck any suggestions please

    1. As a general rule, rummy nose tetras should be kept in a 20 gallon tank in schools of 6-10. They would not do well in a 5 gallon tank because they can get up to 2.5 inches. I would recommend choosing to have a school of 6 neon OR cardinal tetras. And then you can add a snail (Nerite snails are pretty and good for a 5 gallon).

  3. Newbie fish owner here, hello. I just bought myself a 5 gallon tank. I haven’t bought the fish yet but I was thinking of getting 3 rainbow tetra and 1 butterfly tetra. Is it better to keep the same type of tetra or is 2 types alright? Also, would adding ghost shrimp or red cherry shrimp be okay (if so how many for this size tank)? Any help is much appreciated! Thank you!

  4. Any suggestions for a 50-gallon community tank for a beginner.

  5. I have a 29 gallon tank with 3 harlequin rasboras, 3 von rio tetras, a dwarf Gourami, a rubber lip pleco, 2 Amano shrimp, and 2 Nerite Snails. How many cardinal tetras could I get?

  6. Hello Sir,

    I have 6.5 Gallon Tank with 1 Male Betta.

    I am contemplating adding 3 Neon tetras since they actively swim around.

    May I request your opine on this?


    1. Hey there, if you are going to get tetras neon tetras are small and you should get a minimum of 5, which you could possibly get away with. I would get a half dozen shrimp and see what happens, then maybe try 3-5 tetras.

  7. I have a 5 gallon tank and my fish are overpopulating it, but I am not aloud to get a 20 gallon tank. What do I do?

  8. Recently bought 1 Male beta and is on a 3.5 gallon tank, adding some neon tetra would be a good option for the size of tank? And how many. Thanks

    1. I would say no. A 3.5 gallon tank is far too small. They say 1 gallon for every inch of fish and with a betta its probably only big enough for it. You can though get an African Dwarf Frog. They are an amazing option. They are docile and will leave your betta alone. And they only need 1 gallon per frog. Do your research on them, and you can probably have 2 in there.

  9. Hello! I have a 10 gallon tank with 3 Black Neon Tetras and 2 Ember Tetras. I eventually wanted to add up to four Black Neons, Four Ember Tetras, a Honey Gourami and a couple of small Corycats.
    I was wondering if this amount would be alright for a tank of my size? Or should I rethink my plans?

    1. What you are planning sounds good to me! I think that all those fish would be happy with that size:)

  10. I’m getting a 12 gallon long, dem: 35.4L x 8.3W x 9.4H
    I was thinking of getting 6 neons and 6 dwarf corys, is that okay? and Could i add shrimps?

    1. Toby,

      6 Neons and 6 Dwarf Corys are a great choice for that tank size and they are compatible as well. You could add 5-8 shrimps. I would go for Red Cherry Shrimps and/or Ghost Shrimps and also a couple of Nerite or Ivory snails.

  11. I am thinking of getting a 23 litre tank (5 gallons) and would love to get neon tetras. If I got 6 would this be ok then? And are they ok on their own or should I get companions aswell or is tank size too small for that?
    I’m thinking of getting a fluval edge tank – are these ok? Or do you have any better recommendations for this size tank for neon tetras?

    1. Hey Rebecca,
      Fluval edge tanks, even 5 gallon ones, would be great since neons are schooling fish and you would also get an extraordinary visual experience. As a companion, I think one Nerite Snail would be perfect! Nertile snails are great tank cleaners, one of the best algae eating snails around.

      1. Yes but they also repopulate like crazy.

  12. I read above that neons and a Betta were one option for tank mates, but you also say tetras and bettas wouldn’t get along because of the fin nipping some tetras like to do… Are neons the exception and it would work? Looking to put them into a 29 gal, not sure about how many neons? Only other fish will be one pleco that stays small and one adf

    1. Hey Martina,

      Neon Tetras tend to stay around the middle of the tank, out of the betta’s way. That is the reason why they usually tend to get along together. Since you are planning on a 29-gallon tank, I think a school of Neons and Betta will work great for you.

      Tetras are schooling fish so have a minimum of six. With your tank size, I think you should go with twelve of them.

      Plecos tend to stay at the bottom of the tank so it will be great tank mates with betta and neons, as long as it stays small.

      Adf, on the other hand, may not be a good addition, especially with bettas. The main problem that could arise is betta eating all the food before Adf can get to it. It could work since your tank is 29 gallons but ‘feeding Adf’ could be a hassle. So, I don’t recommend it. You should go with a couple of snails instead!

  13. Hi! I recently bought a 6.7 gallon tank how many Glofish tetra can I put in the tank I was going to buy 3 for the tank since they get to be about 2.2 inches long each

  14. Hi!! I’ve just purchased a 5 gallon tank and I currently have 3 guppies.. what other fish can I safely add to this?

  15. Can I put 2 African Dwarf Frogs, 8 Ember Tetras, and 1 Male Betta with a Clown Pleco in a 10 gallon tank?

  16. Hi, I have a betta in a 15L tank and two days ago I added 4 cardinal tetras and 3 snails. The betta has been moping about since they were put in. Have I done the wrong thing? Looking forward to hearing what you think.

    1. Hey, I personally think 15 L tank is too small to have a betta, 4 cardinal tetras, and 3 snails.

      I suggest keeping the betta in a different tank because betta fish need their space. One Betta needs at least about 2.5 gals (9.5 liters) all by itself to thrive.

      I don’t think 15 L tank is big enough to have that many different species, especially with a betta. If the tank was a lot bigger, you maybe could put other species with a betta. However, in my opinion, and any kind of ‘tetras’ is usually not a good tank mate for Bettas since tetras are known to nip fins and what is going to happen is betta will end up attacking and eventually killing them.

      Hope this helps.

  17. Hi, I want to stock my 100l tank with low bioload and docile species. In order for me to maintain good water conditions with weekly water changes, what is my best stocking options? Thanks


  18. Can i keep 20 neon tetra and 20 guppies in a 50 liter planted tank ?

    If no then what should be the ratio ?
    Only guppies and neon tetra of 1 inch size.

    Please assist

    1. B Mahanta,

      Why don’t you start with 4-5 pairs first and see how the fish will do. You can always add more fish!

  19. Hi, I have a 10 gallon tank with 2 guppies, 2 glofish tetras, and 2 African dwarf frogs. Can I add any more tetras? The two little frogs aren’t shy when it comes to feeding time, I’ve seen em beat the fish to the food before.

  20. I have a 35 gallon aquarium I put two bala sharks, two rainbow sharks, two red tail sharks, five barb and six mollys,two sucker fish. I’ll be getting a 120 gallon in a couple of months. Should they be alright for three or four months? They are all small right now.

    1. you are going to have trouble as you should only keep one shark or the will kill until there is only one left. You should research before buying you have made the mistake of not doing this get them out of there and leave only one shark and swap or get some more tanks at least one per shark Bala sharks can be kept together but get huge

  21. Hi i have 4 small gubbies 4 danio zebras 3 red eyes tetra 3 lemon tetras 1 amano shrimp and 1 placo. Placo is out growing the tank and im bout to move him to a bigger tank. I have all of them in a 20 gal tank i wanna know if they are not over crowded on the tank and is it safe to put 2 panda corys and another amano shrimp?? Please help

    1. Hi Julio,
      If you are going to take the pleco out, I think you will be okay. That is quite a variety of species; if it is working out for you, it is quite a setup.

      How often do you clean the gravel and change the water?

      1. I do 25% water changes and every 2 weeks sometimes time
        I do 50 % and i clean the gravel the same time. Idk if that is ok? Im new to the hobby bt im doing all this research about the hobby so i can have more Knowledge on how to care for fishes.

        1. Julio,
          Yes, that is great. That is exactly how I do it. I change approximately 35% of the water while cleaning the gravel, weekly. I do weekly because I have a smaller tank. For 20 gallon tank every 2 weeks is perfect.

  22. can i have at least 23 neon tetras in a 10gal with 2 snails? and also on a 5gal can i have 6 neon tetras and 2 snails?

    1. Hi John,

      6 neons and 2 snails could work in a 5-gallon tank but you might have to change at least 30 % of the water every week. And vacuum/clean the gravel at least once every 7-10 days. 2 snails could contribute to the waste and bioload but if you are regularly cleaning and changing water, you should be good.

      Although neon tetras are fairly small, 23 of them along with 2 snails is not a good idea in my opinion. If you are going to keep 2 snails, considering they are not too big, I would go with about 10 – 12 neon tetras.

      1. That is fine. I had 10 neon tetra and 10 blood fin tetra in a 10 gallon tank.. just change 30% of water every week.

  23. I’m looking into getting a 5 gallon take and I saw that I could put 6 neons and 1 snail. Is it possible to mix different tetras or is that a bad idea?

    1. Ashlee, you can certainly mix different Tetras. But you have to do some research and find out the ones that are compatible. Some compatible ones are Cardinal Tetras and Glowlight Tetras or you can even go with other species like Guppies.

      Neons are shoaling/schooling fish so you have to put them in a group (of at least 3, considering your tank size). Tankmates should be peaceful and not large enough to nip or eat Neons.

      Another thing to consider would be to make sure to pick companion species of fish that are similar in size to Neons. You can go with a little bit bigger tetras like Red-eyed Tetras. I have 3 Neon Tetras + 3 Red-eyed Tetras + 1 Nerite Snail in a 10 gallon tank in my store. I believe the same setup would work for you in a 5 gallon tank as well.

      Some other ones that also go well are Black Skirt Tetras, Painted Tetras, Serpae Tetras, Black Neon Tetras, Silver Tip Tetras etc.

      I hope this helps. After you set it up, please let us know what you went with so the readers/newbie fish keepers have some idea to go by.

      1. I’m back with more questions! How big do barbs get? How many can be kept in a 5 gallon tank? And how many different variations can be kept together!

        1. Ashlee, great to see you back again.

          There are many species of barbs and they do get big for a 5 gallon tank. One of the most popupar barbs, the Rosy Barb gets to be 15 cm (6 inches) long. Black Ruby Barb gets to about 6.5 to 7 cm long. Denison Barbs gets to about 15 cm long. In my opinion 5 gallon tank is too small considering that you have to keep a school of 5 or more of them in order for them to thrive.

          Bigger tanks would be much much better for Barbs. Also consider that they need to be kept in schools of 5-6 or more. They should be kept with fish of similar size and not be kept with slow species specially if the companion species have long fins, as barbs are known to nip the fins of slow moving species.

  24. 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!

    1. 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.

      1. 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!

        1. 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

  25. 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?

    1. 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.

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

    1. 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.

  27. 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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