How Many Fish Can I Keep in a 30L Tank?

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If you have recently acquired a 30L fish tank, or you are considering purchasing a 30L fish tank, you might be wondering how many fish you can keep in it. Unfortunately, you might not like the answer. Although you might have been advised that there are a lot of fish you can keep in a 30L tank, for the fish to be happy, there is only one option.

A 30L tank is the perfect size for a single betta fish. Betta are relatively small in size, and will happily live on their own. Keeping more fish in a 30L tank is not good for their well being. Another option is to consider an alternative like African dwarf frogs or Red Cherry Shrimp. Both of these are also suitable for a 30L tank.

In this article, I want to explain why 30L is too small for most fish, and then I have some advice for keeping a single betta in a 30L tank.

30L is Too Small for Most Fish

Unfortunately, 30L is simply too small for most fish to live in happily. Larger fish will obviously require a bigger tank, and many smaller fish are either very active or live in schools, and these will also require a larger tank.

If a 30L tank is the only option, it’s just about big enough to keep a single betta (also known as a Siamese fighting fish). These are relatively small and will happily live on their own making them perfect for a 30L tank. There’s also the option of keeping other creatures in the tank instead of fish. Cherry shrimp are a great choice. I’ll talk more about both of these further down the page.


If it isn’t too late, you should seriously consider getting a larger tank. A 60L tank will give a lot more options, and your fish will be happier. Larger tanks are easier to clean and maintain too, which is definitely something to consider if this is your first tank. If you’re happy with a single betta, then you will be fine with a 30L tank, otherwise, try to get something bigger.

How Many Fish Can I Keep in a 60L Tank?

So, if I decide to go with a 60L tank, how many fish can I keep in it? Well, the answer depends on which fish you want to keep. Fish vary greatly in size, and how active they are will be a factor too. But to give you an idea, with smaller fish like neon tetra, you will be able to keep around 10 fish in a 60L tank.

A Great 60L Tank for Beginners

If you decide to go for a 60L tank instead, the Fluval Vista 16 (click to check price on Amazon) is perfect for beginners. It’s a nice looking, high quality tank, and it comes with a filter and lots of other accessories, but you will need to purchase a heater, substrate, and plants/ornaments.

Why Shoudn’t I Keep More Fish in a 30L Tank?

You might have heard of the “one gallon per inch” rule when it comes to keeping fish. What this means is for every gallon of water in your fish tank, you can have one inch of fish. Although this might hold true for certain fish, different species have different needs. Some are less active and don’t need as much room, but other fish of the same size are more active and need a bigger tank. You also have to consider how the fish like to live. Some are fine on their own, whereas some need to live in groups. Overall, this is not a great rule to follow and you need to judge it on a case by case basis.

Some people would say you can keep small fish like neon tetra in a 30L tank. The problem is, neon tetra like to live in larger groups and ideally you would want to keep 10 – 15 together. Neon tetra can grow to over an inch, so even going by the “one gallon per inch” rule, you will still be exceeding the limit of around eight inches for a 30L tank.

If you have been to a pet shop for advice, they might have advised that you can keep quite a few fish in a 30L tank. Unfortunately, the staff at pet shops are often not very knowledgeable, and they will sometimes try to sell you more fish because they put profit above the fishes welfare.

Overstocking is a common mistake made by many beginners. They don’t want to break the bank buying a decent sized tank, but still want lots of different fish. And then you see people posting on forums, surprised that their fish has died after just a few weeks or months. Fish need space to move around or they will get stressed, and it’s much harder to maintain the correct water levels and temperature in smaller tanks.

What If I Have a 30L biOrb?

One of the most popular type of 30L tanks are the spherical biOrbs. Although you can still keep a betta in a biOrb, they aren’t ideal. Betta like to spend time near the surface and have a labyrinth organ which allows them to breathe from the surface. Due to the shape of the spherical biOrbs, there isn’t a lot of surface area on the top. biOrbs are quite expensive for what they are too, so if you haven’t yet purchased a tank, I would avoid them if possible, and try to find a shallow rectangular tank which will have a bigger surface area.

Betta Fish: Perfect for a 30L Tank

A single betta fish is perfect for a 30L tank. They are relatively small in size and are happy living on their own. They are tropical fish, and beautiful too, so it definitely isn’t too bad that they are the best choice for a 30L tank!

It is common for bettas to be kept in very poor conditions. Try to rescue one if you can, or purchase from a store where they are well cared for.

What Do I Need to Keep a Betta Fish in a 30L Tank?

  • Tank – I would recommend at least a 30L tank. Not only will the fish be happier, but it will be easier to maintain than a smaller tank. If you don’t already have a tank, the Fluval Vista 8.5 (click to check price on Amazon) is a great tank kit to check out. It comes with lots of accessories, but you will still need a heater, substrate, and ornaments/plants. Betta fish are good jumpers so make sure whichever tank you use has a lid. You should also not fill the tank to the top because betta like to breath from the surface.
  • Filter – Although is is possible to keep a betta without a filter, doing so will require you to change the water very regularly. You will be much better off with a filter. Betta like still water, so you will want to take precautions to make sure the filter doesn’t create too much of a current. The AquaClear 20 (click to check price on Amazon) is ideal for a 30L betta tank because you can adjust the flow, but you will still want to use some foam pads to baffle the filter which will reduce the current.
  • Heater – Betta are tropical fish so they do require a heater. The ideal temperature is between 75 – 80 degrees Fahrenheit. For a 30L tank, a 50w heater like the Eheim Jager is ideal.
  • Plants & ornaments – Putting plants and ornaments in your tank is a great idea. It makes your tank look more attractive and keeps your betta happy. Betta breath from the surface, so make sure to keep the surface clear of plants and ornaments. Before placing any ornaments in the tank, make sure there are no sharp edges that the fish can injure itself on.
  • Water conditioner – Many kits like the Fluval Vista 8.5 come with water conditioner, but if you’re buying things separately you will need to get some. You can find some here on Amazon.
  • Food – Obviously, you are going to need to feed your betta. Don’t buy generic fish flakes because a betta’s diet should be protein rich and they need specific food. You will want to pick up some specifically designed pellets like Aqueon betta food pellets, but they can also eat things like live brine shrimp and mosquito lavae.

Other Creatures You Can Keep in a 30L Tank

If you decide you don’t want to keep a betta in your 30L fish tank, you could consider keeping alternatives like African dwarf frogs or Red Cherry Shrimp.


Unless you want to keep a single betta, 30L is not the ideal size for a fish tank. It’s simply too small for most fish to live in happily. I would advise choosing a larger tank if possible, but if 30L is your only option, it is suitable for a single betta, or alternatives to fish like African dwarf frogs or Red Cherry Shrimp

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