Best Fish For A 3 Gallon Fish Tank

Keeping fish is a hobby loved by millions of people throughout the world. Big or small, there are tanks and bowls for every occasion. For those who want to enjoy fish-keeping without having to deal with humongous tanks and difficult fish, micro tanks (also sometimes known as nano tanks) are a popular option. 3 gallon tanks are small enough to sit on your desk but also large enough to hold more than just plants.

While stocking options for a 3 gallon tank are far less than bigger options, there are plenty of ways to fashion up a tank and make it work. But first, you need to figure out which fish you are going to buy. So let’s have a look at the best fish options for a 3 gallon fish tank.

Why Choose A 3 Gallon Tank?

A 3 gallon tank is considered a nano tank, or a fish tank that holds less than 10 gallons of water. Now, while you have a decent amount of water, there are only a select number of fish that can thrive in such conditions. Since there is not a lot of water, you will need to stick to a maintenance schedule.

But that aside, 3 gallon tanks are small in size, allowing for them to be placed wherever, making them a good choice for those without much living space or children learning how to be responsible for pets. 3 gallon tanks do make it a bit more challenging to create an ecosystem, but that doesn’t mean you cannot create a beautiful mini-garden inside, either.

Many aquarists also use 3 gallon tanks to separate fish. These are ideal for quarantine tanks, breeding tanks, fry tanks, and for holding feeder fish.

Equipment For a 3 Gallon Tank

  • Filter – no tank is complete without a filter to remove harmful debris and chemicals. The lower the water volume, the more a filter will be needed to keep water fresh.
  • Heater – while you won’t always need a heater, tropical fish will enjoy more stable water
  • Lighting System – some plants and fish need to know the difference between night and day.

Top 5 Best Fish For 3 Gallon Tank

As mentioned earlier, a 3 gallon tank is ideal for starting out with fishkeeping, but it is not going to be good in the long term. Though the following fish can survive happily in nano tanks, you should always consider upgrading to more space as they mature.

Without further ado, here are the best fish for 3 gallon tanks:

1. Tetras

Tetra fish

An iconic fish for small tanks. There are several types of tetra fish that are brilliantly colored and tiny enough to have a decent life in a 3 gallon tank or bowl. Keep in mind that tetras are schooling fish, so you will want more than one. You also need to provide these fish with a constantly clean tank, because they can be sensitive to changes in water composition.

Tetra fish also require densely vegetated tanks, since they are native to the Amazon. They also like some darkness, including darkly colored substrate. Be sure to put some driftwood or whatever else to add some shade to their tank. One word of caution: 3 gallon tanks are tiny, so be careful about overcrowding the aquarium.

2. Betta Splendens

betta fish

Also known as Siamese fighting fish, betta fish are another fabulous choice for 3 gallon tanks. These are relatively solitary fish who enjoy warmer waters (so you’ll need a heater) and a weaker current. They also thrive when there are a few decorations and live freshwater plants included in their home. If you have a male betta fish, you should certainly keep them alone. Males—designated by their longer, flowing fins—are more aggressive than females, especially when often the betta splendens breed.

Betta fish are not as hardy as some other fish on this list. They will need more care than some, because they have specific needs, such as filtered water and a wholesome diet. Therefore, it is advised that you take some time to learn more about betta fish before deciding to buy one.

Tetra fish also require densely vegetated tanks, since they are native to the Amazon. They also like some darkness, including darkly colored substrate. Be sure to put some driftwood or whatever else to add some shade to their tank. One word of caution: 3 gallon tanks are tiny, so be careful about overcrowding the aquarium.

3. Fancy Guppies

red and blue guppies swimming

Easily one of the best fish for 3 gallon tank, fancy guppies add a little pop of splendor to the waters of the aquarium. These are also very peaceful fish, so if you have a couple of guppies, you know they will get along just fine. Ranging from 2 to 3.5 cm (0.78-1.37 in) in length, a pair of guppies will enjoy a bowl or tank with some plants and substrate. However, you will want to be careful about which gender you get. Two males (which are smaller than females) are the best choice. Try not to mix males and females, since guppies tend to reproduce faster than rabbits.

Guppies enjoy plant- and meat-based foods, including flakes. Give them a variety to chow down, and they won’t need much anything else but a clean tank.

4. Zebra Danio

Zebra Danio

Are you a beginner to the world of fishkeeping? Then the super hardy danio is perfect for you. These fish are similar in size to neon tetras but don’t have as many parameter requirements. Zebra danio hail from central Asia, India, Nepal, Myanmar and other countries in the same region, meaning they are warm water fish that can grow between 1.8-2.7 in (5-7 cm) long. As long as you keep the water around 65-77 degrees F and maintain a pH of around 6.5-7.2, your danios can live for up to 5 years.

5. Dwarf Oto


There are several species of otocinclus, a kind of catfish, that are not ideal for small tanks. However, the dwarf oto, also called the dwarf sucker, is a great choice for a 3 gallon tank. However, because these fish can grow in size, in spite of being tiny, you may eventually need a larger tank. In some cases, dwarf otos will enjoy some algae, but they are mainly herbivores and love veggies, such as zucchini (courgette), cucumber, and carrots as well.

They are not as active as some other fish on this list, so one or two dwarf suckermouths can fair well in a smaller tank and keep it clean. Oftentimes, they will rest upon objects in the tank or even stick to the glass, so you can see their underbellies.

Honorable Mention: Invertebrates

Because invertebrates, such as crabs, shrimp, fry, and snails, do not move around nearly as much as fish, they are usually the top choice for small tanks. Of course, they are also not as entertaining or colorful. But if you want to have a tank full of life, then consider adding a couple of invertebrates. Shrimp species, like cherry shrimp or Harlequin shrimp, can be kept in groups of 5-8 in a 3 gallon tank.

If you have herbivorous fish, like otos, you can also mix a few shrimp or snails in to keep your fish company. Otherwise, don’t mix the invertebrates with carnivores or omnivores, since they will be defenseless when molting and may fall prey to more aggressive fish.

How Many Fishes In A 3 Gallon Tank?

There is a general rule of thumb used by aquarists to calculate how many fish can fit inside a 3 gallon tank. For fish that are smaller than 3 inches (7.62 cm) in length, you need about 1 gallon of water for 1 inch of fish. This is true if there is nothing taking away from the water volume in the tank, like a large decoration or dry ground. If that’s the case, you need to apply the surface area rule.

In theory:

Let’s assume a 3 gallon tank or bowl is not going to feature anything too large to displace water all that much. Using the 1 inch per 1 gallon rule, you could fit only 2-3 small fish in a 3 gallon tank, assuming those fish do not reach a maximum size of 2 inches (5 cm) or more. For example, neon tetras grow to about 1.75 inches (4.5 cm) max, resulting in a very small school in your tank.

This is why it is better to get fish that are okay with being solitary as opposed to schooling fish, because smaller tanks cannot support the kind of environment some fish instinctively need.

Why Are Goldfish Not On This List?

There are a couple of reasons why you shouldn’t put a goldfish in anything smaller than a 5 gallon tank—and even that is pushing it. First, goldfish pollute water quickly, due to their physiology. This means that a 3-inch goldfish in a 3 gallon tank would only survive in the short term. Since even a common goldfish can grow to about a foot in length (30 cm), you cannot keep goldfish in a bowl or nano tank for too long. In fact, you would need a very large aquarium to keep them healthy.

Therefore, if you want a small tank, you need to abandon the idea of a fancy goldfish. If you want a goldfish, then you need a much bigger tank.


With a little special care and planning, you can create a gorgeous 3 gallon tank. These are some of the smallest tanks on the market, however, so you may have to upgrade in the future. Now that you know which fish are the best fish for 3 gallon tanks, you are well on the way to developing the perfect habitat. So, which fish will you choose?

Do you have experience with nano tanks? Let us know!

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