Best Fish For 5 Gallon Tank (Freshwater and Saltwater)

Are you looking for fish to put in a 5-gallon tank? Well, you’ll be happy to know that there are plenty of options to choose from to identify the best fish for a 5-gallon tank. 

The 5-gallon fish tank is the minimum tank size if you want to keep nano fish in your aquarium. Nano fish are tiny fish that grow less than 2 inches in size.

These smaller tanks are great for most aquarists because of their ease of maintenance, and you can put them anywhere, even on a fish stand.

Also known as a nano tank, these options are becoming more popular for beginner fish keepers looking to enjoy their aquarium hobby. 

Most experienced fish keepers don’t go for 5-gallon tanks because the water temperatures in such aquariums tend to fluctuate more and quickly affect your fish’s health. It also doesn’t offer plenty of swimming space or room for decorations and tank equipment.

While a 5-gallon tank is small for most fish species, it can still be large enough to hold some species comfortably. It is also cheaper to buy and decorate them than larger fish tanks.

Whether setting up a freshwater or saltwater aquarium, we list the best fish you can put in a 5-gallon tank and what you should know before choosing any fish species. 

Factors to Consider when Choosing Fish For a 5 Gallon tank

If you’ve already decided to get a 5-gallon tank, there are still other considerations. There is plenty to think about, from the tank’s shape to the equipment you need before getting a nano tank.

The Tank Shape

Fish tanks come in various shapes, like square, rectangle, or tall tanks. While trying out different tank shapes might seem fun. Some of these designs are hard to stock and decorate for your fish. 

5 Gallon fish tank

Yes, you might find small fish kept in bowls at the local pet store, but that doesn’t mean they’re happy. Even small fish can’t thrive with minimal swimming space. If you’re going for a 5-gallon tank, it’s best to choose a rectangular shape.

It will allow you to add equipment like heaters and filtration systems without crowding. A rectangular tank is also easier to clean and add features like plants and rocks.

Your Fish Size and Behavior

The last thing you want to do is put a fish in a tank that they will outgrow in a couple of months. Not only will they be uncomfortable, but you’ll have to spend more money buying and stocking a larger tank.

School of fish

When buying fish from the pet store, you should remember that most of them are juveniles. Which means they still have time to grow to their full size. 

You must consider your fish’s behavior if putting them in a 5-gallon tank. Some species are very active and love to explore their tank, so they need a lot of space.

The Number of fish

Have you heard of shoaling fish? These fish prefer to be kept in groups rather than alone. They quickly get stressed when they are alone in a tank. Most shoaling fish species are small so that they can comfortably fit in a 5-gallon tank.

For most fish species, however, you might have to keep only one if you choose a 5-gallon tank. Generally, it’s recommended to have one gallon of water for one inch of fish. Another option would be to combine one species with shoaling fish to add some color to your tank. 

While some fish find safety in numbers, others like being left alone and become aggressive to new tank mates. 

You should research the temperament and behaviors of each fish species you want to put in this 5-gallon tank. 

Filtration and Heater System

Now to the equipment. Contrary to what most people believe, fish don’t just need water to survive. All fish species require a filtration system to keep their tank water safe.

A filtration system prevents your fish from nitrate and ammonia poisoning caused by the breakdown of their waste.

Fish Tank Filter

If you’re keeping tropical fish, you’ll need a heater to keep the water warm enough for them to survive. The heater will do all the work for you, so you don’t have to worry about your fish getting temperature shock if it gets too cold.

While such a small tank can limit the number and species of fish you get, there are some fish  who will be happy and healthy with this setup.

Whether you’re looking for freshwater or saltwater fish, you can find the ones that suit you best in the list below: 

10 Best Fish For 5 Gallon Tank (Freshwater)

Although species like betta fish (siamese fighting fish) are recommended for a 5-gallon tank, the best tank size for bettas is between 10 gallons to 20 gallons to keep them healthy and happy.

But here are some freshwater fish you can put in a 5-gallon tank:

1. Guppies

Guppies are one of the most popular tropical fish you can add to your tank. They are peaceful and easy to take care of, so you shouldn’t worry too much about difficulty with keeping them alive. Originating from the tropical waters of South America, these species come in various colors and shapes. 

guppy (millionfish, rainbow fish)

Characteristics of Guppies

  • Have a lifespan of 2 -5 years.
  • Guppies are omnivorous.
  • Grow between 0.6 to 2.4  inches in size.
  • Require water temperatures of between 70-76°F. 

A fun fact about Guppies is they are easy to breed. Guppies do not lay eggs like most fish but give birth to a live fry who can eat and swim immediately after birth. You should only keep male guppies in your tank if you’re not looking to take care of offspring soon. 

They’re great fish for beginner fishkeepers and can survive in a small tank. After they get use to you, you’ll see their playful side when they showcase their beautiful patterns. 

2. Chili Rasbora

The next fish you should consider for your 5- gallon fresh water tank is the Chili Rasbora. It’s a great pick because they only grow up to 0.7 inches in size. These playful freshwater fish are native to Indonesia’s Southwestern Borneo and come in a beautiful red and black color. 

Chili Rasbora

Characteristics of Chili Rasbora

  • They have a lifespan of 4-5 years.
  • Chili Rasboras grow to between 0.6-0.8inches in size.
  • They are omnivorous.
  • Require Water temperatures of between 68-82°F. 

They love schooling, so having one Chili Rasboras can cause loneliness and stress. The thing is, you’ll need 6-8 gallons if you want to keep a school of Chili Rasboras in your tank. 

You’ll be happy having a tank with Chili Rasboras because they are active. You will need a lid for your tank with these fish because they are known to sometimes jump out of the tank. 

3. Neon Tetras

You won’t find Neon Tetras just lounging all over the world. Most Neon Tetras are found in the Amazon river basin of South America. A Neon Tetra is a small fish with a vibrant blue body, red stripes, and markings. 

neon tetra (paracheirodon)

Characteristics of Neon Tetras

  • A Neon tetra has a lifespan of up to 10 years.
  • These fish are omnivorous.
  • An adult Neon Tetra grows to 1-1.5 inches in size.
  • They require water temperatures of between 70–81°F. 

Because they live in streams and blackwater environments, these fish don’t like too much light. The Neon Tetra is a non-aggressive schooling fish, so you can easily keep them with other fish. They are most active during the day when they adjust to their new environment. 

In their tank, you’ll need to add aquatic plants and other habitat features like rocks and sand to keep a neon tetra happy. Their 5-gallon tank will also need a heater to maintain the warm tropical-like temperatures. 

4. Mollies

Mollies are small, self-sufficient creatures who are easy to take care of in a tank. They are freshwater fish originating from Central America. Mollies come in various colors: white, red, orange, and silver. While these fish can survive in a 5-gallon tank, they might have little space to swim around once they reach adulthood.

Characteristics of Molly Fish

  • Mollies have a lifespan of 3-5 years
  • They grow to between 3.5-4.5 inches
  • Molly fish are omnivorous. 
  • They require water temperatures of 72–78°F.

These fish are adaptable to various environments, so you don’t have to be very precise regarding their water parameters. That’s one of the reasons they are a popular fish for anyone new to fishkeeping. If you’re planning on having a community tank, they are a colorful addition.

5. Honey Gourami

Also known as Sunset Honey Gouramis, these beautiful fish are ideal for beginner fishkeepers. They are peaceful fish, native to the freshwaters of South Asia. Honey Gouramis are primarily found in dense vegetation in slow-moving waters like lakes and ponds, so your tank should have plenty of planted features for hiding.

Honey Gourami

Characteristics of Honey Gourami

  • They have a lifespan of 4 to 8 years
  • Gouramis grow up to 3 inches in size
  • Honey Gouramis are omnivorous 
  • They prefer water temperatures of between 71-82 °F.

Only one of these fish can fit in a 5-gallon tank. Although Honey Gouramis are hardy fish, you will need regular water changes to prevent toxins from building up in the tank. 

6. Least Killifish

The Least Killifish are small, making them perfect for a 5-gallon tank. The good thing about these fish is that you can keep a colony of them in a 5-gallon tank, but you have to keep monitoring to prevent stress or diseases. Unfortunately, it would be best if you didn’t keep them with other fish species in such a small tank because it can lead to aggressive behavior. 

Least Killifish

Characteristics of Least Killifish

  • They prefer the water temperature between 66 and 75°F. 
  • The Least Killifish have a lifespan of 3 years. 
  • They are omnivorous eaters. 
  • The Least Killifish grows to about 0.8-1.2 inches. 

Unlike most fish species on this list, Least Killifish originate from the United States. They quickly breed, so unless you want your tank to be a nursery, you should keep only one gender. If you don’t want them lonely, you can add freshwater shrimps or pencil fish to their tank. 

7. Dwarf Puffer

Also known as the Dwarf Pea Puffer, these are among the most popular fish for first-time aquarists. These tropical freshwater have colorful bodies with tiny fins and big eyes. Even when fully grown, these fish are only 1.5 inches so they can fit in a 5-gallon tank. 

Dwarf Puffer

Characteristics of Dwarf Puffer

  • They need water temperatures of an average of 77-79°F.
  • Dwarf Puffers have a lifespan of 4 years.
  • These fish are carnivorous. 

You should know that dwarf puffers aren’t the easiest fish to take care of. They are easily prone to starvation and sensitive to changes in the tank’s water quality. Do not keep males in the same tank because they can become aggressive and injure each other over time. 

8. Scarlet Badis

If you’re looking for a fish that can happily live in a small tank, the Scarlet Badis is an excellent choice. Most adult scarlet badis growing to less than an inch long are ideal for a 5-gallon tank. 

Scarlet Badis

Characteristics of the Scarlet Badis

  • Scarlet Badis grow up to 0.8 inches long. 
  • They have a lifespan of 4-6 years. 
  • Scarlet badis need warm water temperatures of between 72 to 79°F. 
  • These fish are carnivorous. 

Scarlet badis are easy to take care of if you provide proper water quality, diet, and habitat features. They are sensitive to water changes, so 50% of water changes are needed once a week. These freshwater fish are peaceful if you want to add them as tankmates in the future.

9. Rosy Loaches

Rosy loaches are tiny fish that belong to the Botia family. These fish are beautiful and can quickly adapt to new environments, including a 5-gallon tank. Rosy Loaches are native to Myanmar and can grow to a length of 1 inch to 1.2 inches, so you don’t have to worry about space.

Rosy Loach

Characteristics of Rosy Loaches

  • They can go to a maximum size of 1.4 inches.
  • Rosy Loaches need the water temperature at 70 to 79°F. 
  • These fish have a lifespan of 5 to 7 years. 
  • Rosy Loaches are omnivorous. 

These fish need an aquarium filled with plants and rocks because they are active fish who love to swim constantly. They also prefer dim lighting because it’s similar to their natural habitat.  To reduce any aggressive behavior, it’s recommended to keep Rosy Loach in schools of 8-10. 

10. Cherry Shrimp

You should consider a cherry shrimp if you’re looking for another invertebrate to add to your freshwater aquarium. These freshwater shrimps come in different color variations, with red shrimps being the most popular. 

Cherry Shrimp

Characteristics of Cherry Shrimp

  • Cherry shrimp have a lifespan of 1-2 years. 
  • They are omnivorous.
  • These shrimp can survive in water temperatures of between 65 – 85°F. 
  • They grow up to 1.5 inches by the time they are adults. 

The good thing about Cherry shrimp is they require very little space to be comfortable. However, you need to add plenty of vegetation and surfaces where they can eat off. Like other freshwater creatures in a small tank, you will need to carefully monitor their water conditions to prevent disease or stress. 

10 Best Fish For 5 Gallon tank (Saltwater)

Maintaining a saltwater aquarium isn’t easy for any aquarist because saltwater fish need large amounts of water, just like in their natural habitat – the ocean. 

Ideally, you don’t want too many saltwater fish in a single nano tank. Saltwater fish need more space to swim, play, and feel comfortable. 

But as you will see below, plenty of saltwater fish species can survive in a 5-gallon tank.

1. Flaming Prawn Goby

The flaming prawn goby is one of the best fish for a 5-gallon saltwater tank because of their small size. Despite their long name, these fish are tiny, with an adult growing up to 1 inch in size. With their origins in the Indo-pacific, these saltwater fish are very peaceful and easy to take care of.

Flaming Prawn Goby

Characteristics of Flaming Prawn Goby

  • They are carnivores.
  • An adult grows up to 1 inch in length.
  • The best water temperature for these fish is 25°C.

Their uniqueness and outstanding colors will make any tank beautiful. Your Prawn goby needs planted tanks filled with rocks because they can sometimes be timid and need places to hide. These fish will be great to have if you have experience with maintaining saltwater aquariums.

2. Tailspot Blenny

Like many saltwater fish, the Tailspot blenny originates from the Indian and Pacific oceans. They are tiny and inexpensive fish that can survive in a nano aquarium. Tailspot Blennies are colorful and active fish that can also help if you have an algae problem in your fish tank.

Tailspot Blenny

Characteristics of Tailspot Blenny

  • They grow to a maximum size of 2.5 inches.
  • Tailspot blennies require water temperatures between 78 to 82°F. 
  • Blennies are herbivores. 
  • These fish have a lifespan of 3 to 5 years.

Blennies are very hardy fish who can live a long, healthy life with proper care. They can sometimes play dead when stressed, so don’t be surprised when you find them laying at the bottom of the tank. They can also exhibit aggressive behavior to their related species, so it’s best to keep only one Blenny per tank. 

3. Hector’s Goby

Hector’s goby is a small marine fish originating from Fiji, Indonesia. They require a bit more experience to take care of, but they’re very peaceful. Their bodies have a dark blue base color with yellow stripes at the top. Their tank will need to have plenty of rocks as hiding places to keep them happy. 

Hector's Goby

Characteristics of Hector’s Goby

  • They grow up to 3 inches in size. 
  • Hector gobies are omnivorous. 
  • They have a lifespan of 2-3 years. 

These fish will sift through sand while looking for food in their natural habitat. Their diet mainly consists of a variety of brine shrimp, mysis shrimp, and live worms. For a 5- gallon tank, it’s best to keep only one hector goby. 

4. Mini Dart Goby Fish

They are the perfect fish for small tanks because an adult Mini Dart Goby fish grows up to 1 inch in size. These schooling species are playful and usually don’t bother their other tank mates.

 You’ll find these goby fish sticking together, so putting a school of 3 to 5 together is best.

Mini Dart Goby

Characteristics of Mini Dart Goby Fish

  • These fish grow up to 1 inch in size. 
  • Goby fish have a lifespan of around 1.5 years.
  • They are carnivorous.

While they seem easy to take care of, they are not beginner-friendly. Mini Dart Gobies are picky regarding their food, even though you need to feed them multiple times daily.

 With a relatively short lifespan, you need to be extra careful about their needs, especially water parameters like temperature.

5. Banggai Cardinalfish

The Banggai Cardinalfish is a commonly available saltwater fish that you can take care of in your home aquarium. The distribution of this fish is mainly restricted to the Banggai Islands in Indonesia. These tiny species are beautiful, with small white spots on their body and fins.

Banggai Cardinalfish

Characteristics of Banggai Cardinalfish

  • They require water temperatures of between 73 to 84°F. 
  • These Cardinal fish grow to between 1.2-3 inches in size.
  • They are mainly carnivorous. 

The Banggai Cardinalfish require minimal lighting and are compatible with reefs. The females have rounded bodies and are generally smaller than their male counterparts. They can hide for a day or two, so give them time to adjust comfortably to their new tank environment.

6. Firefish Goby

The Firefish Goby is an outstanding saltwater fish for a 5- gallon tank. You likely find these fish swimming in the reefs of Hawaii and other parts of Africa. Firefish gobies are a peaceful fish and very active during the day. Their name is because of their red-orange color and has nothing to do with their temperament. 

Firefish Goby

Characteristics of Firefish Goby

  • They grow up to 3 inches in length.
  • Firefish goby requires a water temperature between 72 to 80°F.
  • They are carnivores. 
  • Firefish Goby has a lifespan of about 3 years. 

If you plan on adding these fish to your tank, you should also add a lid. Their lifespan is sometimes cut unfortunately short because they like jumping out of their aquariums. Firefish gobies will be happy with sand and rocks to hide in their tank. It’s recommended to have only one firefish goby per 5-gallon tank. 

7. Yellow Line Goby

Another fish from the Gobiidae family you can have in your 5-gallon tank is the yellow line goby. They have yellow lines on their bodies and are a great addition because they are cleaner gobies. Cleaner gobies are beneficial to any marine tank because they remove parasites from the aquarium. 

Yellow Line Goby

Characteristics of Yellow Line Goby

  • They require water temperatures of between 75 to 82°F.
  • Yellow line Gobies are carnivorous. 
  • They grow to a maximum length of 1.5 inches. 
  • These fish have a lifespan of 2-4 years. 

The Yellow Line Goby is native to Brazil and small enough to fit in a 5-gallon tank. You’ll have an easy time caring for these fish because they are calm, but be warned, they love jumping out of their tanks too!

8. Neon Blue Goby

The Neon Blue Goby is similar to the Yellow Line Goby, except for their appearance. Unlike the Yellow, Neon Blue Gobies have a vibrant blue line on their bodies. They are also cleaner gobies to help keep the tank clean and healthy. 

Neon Blue Goby

Characteristics of Neon Blue Goby

  • An adult Grows up to 2 inches in size. 
  • They have a life expectancy of 1-2 years. 
  • Neon Blue gobies are carnivores. 
  • They need water temperatures of between 72 to 78°F. 

Originating from the Caribbean, you’ll find these fish easy to care for if you stick to the proper water parameters. You should also ensure they have a good environment with good water quality, a high protein diet, and plenty of hiding spots.

9. Green Clown Goby

Another Goby fish you can put in a 5-gallon tank is the Green Clown Goby. These fish are calm, and their bodies are green, orange, and yellow. Like other gobies, they originate from the Indo-pacific region, making them reef compatible. 

Green Clown Goby

Characteristics of Green Clown Goby

  • They are carnivorous. 
  • Green Clown Gobies grow to a maximum of 1.75 inches. 
  • They prefer water temperatures of between 72-78°F.
  • Green Clown Gobies have a Lifespan of 2-4 years

Due to their small size, these fish don’t have a lot of filtration needs. However, saltwater fish need more water to survive. They can coexist with other peaceful tankmates as long as they aren’t taking up too much space in the 5-gallon tank. 

10. Red Head Goby

The Red head Goby is a beautiful fish with bright red, yellow, and white markings. They originate from the Indo-pacific region, making them also reef compatible. These cute fish also help maintain the quality of the water for other species in the aquarium. 

Redhead Goby

Characteristics of Red Head Goby

  • They are carnivorous. 
  • Red Head Gobies grow to a maximum of 1-2 inches. 
  • They prefer water temperatures of between 72-78°F.

Although they are peaceful fish, they can be territorial about their space towards their own species. You should ensure to feed these gobies small amounts of food at least twice per day. Their diet consists of brine shrimp, bloodworms, and frozen mysis shrimp.

Saltwater fish often need a large amount of water like in the ocean. So keeping them in a small tank can cause aggressive behavior in the long run.


Hopefully now you have an idea of which freshwater or saltwater fish you want for your nano tank.

The 5-gallon fish tank option is suitable for aquarists who understand water parameters and the nitrogen cycle to keep the water safe for their fish.

While these tanks are ideal for aquarists with a small budget and limited space, increasing your tank size will significantly improve the quality of life of your fish.

Leave a Comment