Best Fish For 3 And 3.5 Gallon Tanks

If you’re just starting out as an aquarium keeper, chances are that you want to start small. Small fish tanks seem like they’d be easier to care for, and they don’t take up much space.

The reality is that a three or three-and-a-half-gallon tank can be more difficult to care for than you anticipated. One reason for this is that few fish will fit in this small of a tank.

Not sure which fish you can choose for your small tank? That’s okay, we’ve created a list of the best fish for 3 and 3.5-gallon tank.


Guppies are one of the best fish to keep in nano tanks because they stay small. They are active and fairly easy to care for, making it simple to liven up even the smallest tanks.

The best part is that guppies are not schooling fish, so you don’t need to try and crowd a bunch in a small tank.

Just make sure that you keep a tank of only males or only females as they are active breeders. If you keep a mixed-gendered aquarium, you’ll find yourself overwhelmed with baby guppies.


Endlers’ livebearers look like guppies, but they stay even smaller. In fact, they prefer to live in smaller environments than large ones. This makes them perfect for a nano aquarium.

They also come in brighter colors than guppies, so they will make your aquarium stand out even more. Like guppies, you should be careful to only keep one gender in your small tank.

Ember Tetras

Tetras aren’t normally a good option for nano tanks. Most tetras reach about two inches in length and are schooling fish. Because they’re schooling fish, you need to keep at least six in a tank. This would be too much of a bioload for a tank this small.

But, ember tetras are one of the smallest species of tetras, so they are perfect for a smaller tank. They’re also a fun fish to keep in your aquarium because of their bright orange color.

With that said, these aren’t the best fish for beginners. They’re more sensitive to changes in water quality. It’s harder to keep the chemistry stable in smaller tanks than in larger tanks.

Neon Tetras

Neon tetras are another small tetra that can make a good addition to your nano tank. Not only are they small, but they are one of the most popular community fish on the market.

This is because of their bright blue and red coloring that truly makes them stand out. Want something a little different? You can also get black neon tetras that have black and white contrasting colors.

Neon tetras are social schooling fish, so you’ll need to keep at least six in your tank.

They’re slightly bigger than ember tetras, so they would do better in a 5 or 10-gallon aquarium. But, if you give them a nice setup, it’s possible to make them happier in a smaller space.

Chili Rasboras

Chili rasboras look similar to ember tetras because of their bright orange coloration. But, they also have a long streak of black down their sides, along with spots of black on their fins.

They are schoaling fish, so you’ll need to keep a school of at least six in your tank. Luckily, they are also one of the smallest fish on this list, so that’s workable to do.

White Cloud Mountain Minnow

White cloud mountain minnows are another small schooling fish. They’re also very easy to care for. They are hardy, cold-water fish, so you don’t even need to provide them with a heater.

With that said, they prefer a lot of open space, so they aren’t the best option for a nano tank. But, if you set their aquarium up right, you can keep them happy.


Otocinclus are a type of catfish, a bottom feeder that is wonderful for controlling algae. They aren’t as active as some of the other fish on this list. But, they are adorable little critters that will stick to the sides of your tank.

Most people buy otocinclus to help clean up their schooling tank. But, otocinclus are schooling fish themselves, so you need to keep a group of at least six. Because of this, they will need to be the only species in your tank.

Betta Fish

One of the best fish to keep in a smaller tank is a betta fish. Generally, you should have at least five gallons for a betta, but some do very well in a smaller tank.

Bettas have big personalities, and some of them will get stressed in five-gallon tanks or bigger. But, you should never place a betta in anything smaller than a three-gallon tank. Three gallons is the absolute smallest they should live in.

Bettas are a wonderful choice for beginners because they’re hardy and easy to care for. They have beautiful, bright colors, and they are full of personality.

Least Killifish

Least killifish are one of the best fish for nano aquariums. They are one of the smallest fish in the world and thrive in small spaces. Best yet, these little fish can live up to six years!

Like guppies, these fish are livebearers, so you should only keep one gender in your tank.

Pygmy Gourami

Gourami are stunningly beautiful fish in the same family as the betta fish. Most gouramis are far too big to fit in a three-gallon tank, but pygmy gouramis stay nice and small. They are very energetic, but peaceful fish, so they’re a great choice for small aquariums.

Pea Pufferfish

Pea pufferfish are one of the most adorable little fish you can keep in a three-gallon aquarium. Like their saltwater cousins, they can puff up. They only do this when they’re stressed out, though, so you should avoid trying to make them puff up.

The problem with these fish is that they are not good for beginners. They are very sensitive to medications and aquarium chemicals. They should only be kept by those with a bit of experience.

Bumblebee Goby

Bumblebee gobies are another unique little fish with beautiful black and yellow striping. They are a shy species, so they’re not as active. But, they like to live in groups, so you’re more likely to see activity.

Cherry Shrimp

Cherry shrimp aren’t fish, but they make the perfect addition to any tiny tank. Shrimp are so fun to watch, and because they’re so small, you can house many of them in a three-gallon tank.

Better yet, there are other similar shrimp that come in other colors. So, you can get a variety of colors from red, yellow, green, blue, and black.

Ghost Shrimp

Like cherry shrimp, ghost shrimp are a good choice for nano tanks. They aren’t as colorful, but they are active and incredibly cheap. They do grow larger than cherry shrimp, so you can’t keep as many in your tank.

Thai Micro Crabs

If you like invertebrates, Thai micro crabs will make a good addition to your nano tank. They can be hard to see, but they’re low maintenance, and it’s fun to watch them crawl over decorations and plants. If you want to add a little “pop” to your tank, you can consider adding a few of these crabs in with your fish or shrimp.


We hope that you enjoyed this list of small fish for nano tanks. If you enjoyed it, be sure to share it with other beginning aquarium keepers.

It can be hard to find fish for a small tank, but the truth is that you have more options than you’d expect.

Any one of these fish would be a good option for your nano tank. Just make sure not to overcrowd your tank or your fish might become unhappy. Good luck!

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