Nano Tank Fish 101: Complete Guide (2022)

The Ultimate Guide for Nano Tank Fish Owners

If you’re someone who doesn’t have a lot of space but still wants to keep fish as pets, you should look into owning a nano fish tank. As the name implies, a nano fish tank is meant for nano fish. That’s why it’s smaller than your usual aquarium. Owning nano tank fish is great if you’re living in a small apartment. Whether you decide to place the tank in your bedroom or the lounge, having a little fish in your small aquarium is sure to liven up the place.

This ultimate nano tank fish guide has been created to cover everything there’s to know about nano tanks and fish. We cover the benefits of such a tank, the types of nano fish you can keep in it, how to properly maintain such tanks, and a whole lot more. Whether you already own a small tank or are a beginner fish pet owner, this guide will prove helpful to you.

So, let’s begin!

Nano Tank Fish

What is a Nano Tank?

Let’s cover the basics first. A tank is described as a nano one if it holds approximately 30 gallons of water or less. Due to how they are built, such tanks are only meant for housing small fish or other water creatures (shrimps, water snails, and more).

Such tanks are designed to be easily placed on tables, desks, or other small stands. A lot of people tend to put such tanks on their work desks. You can also find such tanks being used to decorate certain art installations, book stores, coffee shops, and such. Nano tank fish are all about offering beauty and satiating a person’s fish-keeping hobby without demanding a lot of space.

Of course, there are pros and cons to owning this type of fish tank. This guide covers the accompanying benefits and disadvantages as well.

Depending on what you’re looking for, such tanks for nano fish are available in a variety of designs. You can use such a tank for freshwater or saltwater creatures.

Below is a list of the types of nano tanks you will find. Take your time to do the proper research to find a tank that best fits your needs.

When it comes to a nano cube aquarium, you will notice that this type is symmetrical. This is one of the most popular small tank models people go for. The four sides and the bottom are made of glass walls while the top is open. Depending on the model it can come with a mesh screen or a plastic lid to prevent fish from jumping out or something falling into the tank.

These kinds of tanks come in a variety of sizes. You can even select a small one that holds just 3 or 5 gallons of water.

While many people like such tanks because they don’t need a lot of space, many fish pet experts recommend against buying them, especially if you plan on keeping a lot of fish. This is because the shape of a cube tank decreases gas exchange. Compared to a rectangular aquarium, a cube-shaped model limits the amount of water surface for gas exchange, even if the amount of water in both tanks is the same. A good amount of gas exchange is vital for the health of your fish.

Not only that, a cube-shaped tank isn’t recommended for fish that require a lot of area to swim around in. So, if you’re in the mood to buy such a tank, you should consider putting fish that don’t swim frantically and are more into hovering or are rock-dwelling nano fish.

  • Nano rectangular aquariums

As the name suggests, these tanks have a rectangular shape. As already mentioned, a rectangular shape allows for better gas exchange due to more surface area of water at the top. And while they can house more fish, they will take up more space compared to a nano cube tank even if the volume of water remains the same.

Such types of tanks are great for fish that like to swim a lot. The rectangular construction also gives you more area to place decorations.

  • Nano saltwater aquariums

Nano saltwater aquariums are used for those wanting to create a nano marine environment. These types of tanks are meant for saltwater fish. They are perfect for bringing a bit of the ocean into your house or workplace. Such tanks usually come with their own equipment and materials to help create a saltwater environment. Not only that, but such tanks can be used for placing oceanic live rocks.

For those who might not know, a tank that contains only fish and live rock is known as a FOWLR, which is short for Fish-With-Only-Live-Rock. Live sand is usually used as a substrate in this type of tank.

Talking about saltwater nano tank fish aquariums, they can lead to the creation of a nano reef aquarium. To keep things simple, a nano reef aquarium is a type of tank that includes reef creatures, live coral, and live rock. You will usually get to see a variety of fish, crabs, snails, sea urchins, starfish, and more in such an aquarium. A reef aquarium can be a gorgeous addition to your home if looked after properly.

  • Nano freshwater aquariums

Coming to the freshwater side, a freshwater nano tank is used for hosting freshwater creatures. These are the type of nano tanks that can house a variety of plant life, depending on the kind of aquarium aesthetic you’re going for.

You should take your time to think about the type of fish and environment you want to have in your nano fish tank. If you’re going to have a lot of fish with water plants, rocks, and other decorations, opting for a rectangular tank will be beneficial.

The Equipment Required by Nano Tank Fish Owners

To create the perfect nano fish tank environment, you need to understand the importance of having the right equipment to meet your goal. The wrong equipment will not only cost you extra money on replacements, but can even result in the death of your pet fish. And you don’t want that, right?

You will require lights and a filter regardless of if you have a saltwater or freshwater tank setup. Depending on what you want to keep in the tank, a heater might also be necessary.

To help you out, here’s a list of equipment required for a nano fish tank!

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You can’t have a healthy fish tank without a filter. A tank filter works to ensure the water remains clean. Due to the small size of nano fish tanks, they are vulnerable to getting dirty much quicker than larger tanks. Not only do filters help keep the water clean, but they also offer a level of water flow inside the tank. Depending on the size of a tank, you might need to install a powerhead to help with better water flow.

If your nano tank doesn’t have a built-in filter, you will need to buy a separate filter. You can opt for a hang-on-back filter to provide your tank with chemical, biological, and mechanical filtration.


Yes, your fish and other creatures inside the tank require light to thrive. If your nano fish tank doesn’t come with built-in lights, you will need to buy separate lights. Lights are necessary for aquariums to help mimic the natural day and night cycle. Not only that, but lights are also crucial for proper plant growth inside the tank.

LEDs are considered the best choice for lighting tanks. They are small and can help with reducing heat build-up. A number of current nano fish tanks come with LED lighting.

The proper lighting also assists with making your nano fish appear clear so you can keep an eye on any illnesses breaking out in the tank. Lights also play a role in making everything inside the tank shinier and brighter, leading to more visual appeal.


A heater is required for tropical fish to thrive. It will do its job to ensure the water temperature remains consistent and your fish and other critters inside the tank remain comfortable. You should keep in mind that fish aren’t able to regulate the temperature of their bodies themselves, so it’s essential to monitor the temperature of the water when seasons change.

Don’t hesitate to talk to your local pet shop employee to gain more information about the equipment you might need as a new nano fish tank owner. There are complete nano fish tank kits available that include a filter, light, and more items.

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How To Set Up a Nano Tank Fish Aquarium

Are you ready to bring a nano tank fish into your home or office space? Let’s go over the steps you should keep in mind when you’re prepared to keep nano fish as pets.

1. Select a Location

The location of your nano fish tank is very important. While a particular table or counter might seem like a good idea, you should keep in mind that a nano tank will get very heavy after you fill it up with water. Also, continuously moving an aquarium isn’t recommended. You should also consider placing the tank in an area with a good amount of natural light to prevent algae growth.

Do you want the tank on top of your work desk? Should it go in the lounge? Do you want to place it on a table in the bedroom? Should it be placed in an area that your cat can’t easily get to? Take your time to think about these questions properly

The space you select for your nano fish tank will also help determine the size of tank you should buy.

2. Clean the Tank

Even if you just bought a tank from a pet or hobby shop, you should still give it a good cleaning once you bring it home. If you happen to buy an already used tank, it’s recommended to clean the tank with a mixture of vinegar and warm water.

3. The Decorations

The number of decorations you can place inside a nano fish tank depends on the tank’s size. You need to leave room for your fish. So, you shouldn’t go overboard with the decorations and make it a mess inside. Remember to add gravel or sand inside the tank, too. Depending on the kind of fish you want as a pet, you will need to add substrate as well.

Adding live plants or corals inside the tank can also help add a pop of color to a nano fish tank.

4. The Equipment

If your nano fish tank doesn’t come with built-in equipment, make sure you install the equipment before filling the tank with water. Remember to carefully read the instructions to ensure the equipment functions the way it’s supposed to.

5. Time to Add Water

Once everything is done, it’s time for you to add water into the tank. However, you need to know what type of water to add.

Saltwater and freshwater tanks need different types of water. You might need to re-mineralize water depending on the type of fish you plan on keeping. For example, a nano reef tank requires salt.

When it’s time to add water into the tank, you shouldn’t pour all of it at once because doing so can lead to the sand becoming displaced. It’s recommended that you place a small bowl inside the tank (on the sand) and then fill up the bowl to ultimately fill up the tank.

6. The Nitrogen Cycle

The nano fish tank should undergo a nitrogen cycle to promote bacterial build-up to protect fish by converting ammonia and nitrites. The rocks and substrate inside the tank assist with bacterial growth and overall management of the nitrogen cycle.

7. Release the Fish!

Don’t immediately release the fish into the tank. The little beings are entering a new environment. So, you should give nano fish time to get used to their new surroundings. It’s recommended that you allow the fish to stay in the bag they came in for a while.

Here’s what you should do:

  • Allow the bag that the fish came in to float on the surface of the tank for at least 10 minutes.
  • Now, open the bag and add a cup of water from the tank inside the bag. Remember to reseal the bag.
  • Allow it to float for another 10 minutes.
  • Now, add another cup of tank water.
  • Keep repeating until the original fish bag is full.
  • Now, you can transfer the fish by using a net.
  • Make sure not to pour the water that’s inside the bag into the tank!

It’s recommended that you keep the light off for a couple of hours, to help the fish adjust to their new tank.

Nano Tank Fish Aquarium Maintenance Guide

After setting up your nano fish tank and adding the type of fish and other creatures you want to house in it, proper nano fish tank maintenance can’t be ignored. Fish need to be cared for the same way you would care for another pet. This means that you need to ensure the tank remains clean to keep the fish inside healthy and happy.

Do not be fooled by the small size of a nano tank. Having a small fish tank in your house doesn’t mean it will be easier to maintain than a bigger aquarium. You should keep in mind that the small size of a nano fish tank, and less amount of water, leads to quicker build-up of contaminants.

Below are some steps you should follow for proper nano fish tank maintenance. Remember that you’re the one who decided to give a bunch of fish a new home and be responsible for them. The least you can do is give your nano fish a healthy tank to live in.

We have divided the maintenance guide into daily, weekly, and monthly tasks.

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  • Daily Nano Tank Maintenance

You should make it a habit to take care of your nano fish tank daily. Don’t worry because the process won’t take long. Daily maintenance tasks play a role in determining the overall health of the tank in the long run.

So, start observing the tank daily. The more familiar you are with the tank, the better you will be at noticing changes that can cause harm to the tank. While observing the tank, look at whether or not your nano fish are active. Did you see anything different about their color or fins? Discoloration in fish and inactivity can be signs of illness. Also, notice the color of the corals if you have a nano reef aquarium.

Of course, you should take a look at the color of the water as well. Does it need to be changed?

Depending on the type of nano fish you own, don’t forget to feed your fish daily. Overfeeding fish can lead to increased nitrate levels though, so prevent overfeeding. Phytoplankton can also be bought for feeding corals and other microorganisms inside the tank.

See if the glass needs cleaning, too. Ignoring cleaning it can lead to hard algae build-up and harm the tank’s inhabitants.

Also, look at the equipment. Is the temperature at optimum levels? Is the filter working?

  • Weekly Nano Tank Maintenance

At least once a week, you should be testing water parameters. The condition of the water inside the tank is crucial for determining the health of the fish inside. A stable tank is what you need to ensure the longevity of your pet fish, other critters, and plants. Also, a stable tank means that it will require comparatively less maintenance than trying to salvage an unhealthy tank environment because you ignored the little signs.

Keeping up with your weekly tank maintenance tasks can give you some free time by moving certain tasks to next week because your tank is healthy. Consistent testing helps fish owners detect any imbalances that might cause trouble down the road. There’s a variety of water testing kits readily available to help you take care of your fish.

Your weekly testing should include water changes, too. You can’t leave the fish in the same water for months. Nano fish tank water will need to be changed regularly to keep your fish healthy, because a tank filter can only do so much. Water changes will also assist with getting rid of contaminants and help prevent algae growth. It’s recommended that you change the water in your nano fish tank at least every other week.

When emptying the tank, make sure to scrub down the glass walls before refilling the tank and putting your fish back in it. Many pet owners will also change the gravel or sand used in the tank before filling it up again.

  • Monthly Nano Tank Maintenance

When it comes to the monthly maintenance, it’s important to change the filter media at least once a month. A high-quality filter is essential to keep the water inside a fish tank clean. However, due to nano fish tanks getting dirtier faster, the filter can get dirty faster, too. So, make sure you clean your filter every month.

What Kinds of Nano Tank Fish to Buy?

Knowing about the correct type of nano fish to house in a nano fish tank is vital if you want to continue keeping nano fish as pets. As mentioned in this guide, a nano tank is meant for nano fish. Putting bigger fish in it will lead to problems.

Nano fish are quite beautiful to look at and will look wonderful swimming around in the tank whether you place it in a bedroom or a study desk.

Below is a list of vibrant nano tank fish that will make your aquarium look visually appealing.

1. Chili Rasbora

Chili Rasboras are some of the smallest fish out there. As the name implies, the adults are fiery red in color while the younger ones are paler. If you happen to buy younglings, you will get to see them mature and display their bright color in approximately six months. These fish can grow to become around 0.8 inches long and are pretty slender.

Due to their very small size, it’s recommended that you have a bunch of them in your nano fish tank. These red fish look fantastic swimming around against a background with live plants.

2. Green Neon Tetra

The Green Neon Tetra can grow up to 1.25 inches. As the name states, this species features bright blue-green, horizontal stripes that shine a lot. They can easily live in a tropical tank environment. You can easily house a bunch of them in a nano tank.

3. Ember Tetra

While you can’t have an actual adult goldfish in a small nano tank, it doesn’t mean you can’t have a gold-colored nano fish as a pet. The Ember Tetra is an excellent alternative to goldfish. They can grow up to 0.8 inches, which is very small compared to how big an adult goldfish can get. A school of Ember Tetra is a great way to add an exciting pop of color to a bigger nano fish tank. They are also quite active, so you will get to see them happily swim around the tank as you relax.

4. Gertrude’s Spotted Blue Eye Rainbowfish

Yes, you can have Rainbowfish in a nano fish tank, too, if you know which species to go for. The Gertrude’s Spotted Blue Eye Rainbowfish can grow up to 1.5 inches long. They have a yellow or a light blue body featuring black spots and lovely bright blue eyes.

The Blue Eye Rainbowfish males tend to be more colorful than the females. It’s recommended that you keep two females for one male in a tank. Having more than one Blue Eye Rainbowfish male in the tank can lead to a sparring match between the two to impress the females.

They can live in a variety of tank environments. However, they prefer high pH levels. They also like to stick close to the surface. So, make sure that your nano fish tank has some sort of secure lid on it.

5. Scarlet Badis

The Scarlet Badis can grow up to 0.8 inches long. They are considered to be one of the most beautiful nano fish. They are usually red or orange, with neon blue shades on the dorsal fins. They are known to be quite peaceful toward other fish.

Feel free to talk to your local nano fish supplier to see which type of nano fish would be perfect for the kind of nano fish tank you own. Proper tank maintenance can help increase the longevity of your nano fish.

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Nano Tank FAQ

What is considered a nano tank?

Aquariums capable of holding up to 30 gallons of water are considered to be nano tanks. The design of nano fish tanks is generally quite compact because they are not supposed to demand a lot of space. They can be easily placed on various desks, tables, and stands. Nano tanks are meant for housing nano fish or other small water creatures. They’re an excellent way to have pet fish if you live in a small apartment or want to have fish around in an office cubicle.

What is the smallest nano fish?

As of writing this nano tank fish guide, the smallest nano fish is the Indonesian Super Dwarf of the Paedocypris Progenetica. Being the smallest species of freshwater nano fish, the male Indonesian Super Dwarf is known to grow only 0.39 inches or 0.99 cm. The adult female of this species has been recorded to grow up to a maximum of 0.41 inches (1.04 cm). Basically, this tiny fish is more or less the size of a mosquito.

If you’re thinking of keeping this type of nano fish, you can keep a school of them in a tank that’s able to hold 5 gallons of water.

How many fish can be in a nano tank?

It’s recommended that you stick to the 1-inch of fish per gallon of water rule to prevent overcrowding and an unhealthy tank environment. So, if you own a 3-gallon nano fish tank, you can add three 1-inch-long fish in it. If you’re thinking of adding other things into the tank as well, for example, a water snail, etc., you can decrease the number of fish to compensate.

Also, the 1-inch rule applies to the adult fish size. This means that you shouldn’t add the type of fish that will grow larger than an inch or two as time passes in a small tank. Nano fish, depending on their species, will likely only grow up to 2 inches. So, you will need to have the appropriate nano fish tank to take care of them.

Are nano tanks easy to keep?

One might assume that nano fish tanks are easy to keep because they are smaller than traditional tanks. However, you should understand that due to the smaller size of nano fish tanks, such aquariums are vulnerable to getting dirtier faster. That’s why such tanks are considered to be a bit harder to maintain than larger models. Not only that, but because nano tanks have less water in them, controlling and maintaining the perfect temperature and pH inside the tank can be tricky. Nano reef tanks can be harder to take care of than non-reef environments.

That’s why it’s important that you follow the recommended steps for proper nano fish tank maintenance to ensure the longevity of your fish.

Is a betta a nano fish?

Since Betta fish can grow up to 3 inches in size, they aren’t technically nano fish. However, many fish pet owners consider Betta fish as nano fish due to their small size and ability to live inside nano fish tanks.

If you are thinking of adding Betta fish in a nano fish tank, there are certain things you should keep in mind. For a single Betta fish, it’s best to go for a tank that can hold 3 gallons of water (at minimum). A smaller tank can result in your Betta fish growing bored. Due to Betta fish being very territorial, do not try to house two Betta in the same 3 or 5-gallon tank. Doing so can result in the two fish fighting each other, resulting in severe injury or even death of one or both fish.

Wrapping It Up

Nano tank fish can be a great way to keep fish as pets without having to worry about space. Just ensure that you stick to a proper maintenance routine. Also, feel free to talk to your local nano fish supplier to see which type of nano fish would be perfect for the kind of nano fish tank you own.