How Many Fish in a 5-Gallon Tank? 15 Fish For a Small Tank

If you’ve done some research on fishkeeping, you’ve probably noticed that a standard tank size is 10 gallons. What about smaller sizes? How many fish can be in a 5-gallon tank and are there species that prefer this size?

No matter whether you don’t know where you’d put a larger tank or you simply like the appearance of smaller aquariums, there are many reasons why you’d get a 5-gallon tank. However, there doesn’t seem to exist much information about fish that prefer small tanks.

While this might discourage many people new to the fishkeeping hobby, I am here to give you hope. Many fish species can thrive in a 5-gallon tank!  

So, if you’ve caught yourself wondering, “How many fish in a 5-gallon tank?”, this article is for you. Keep on reading – I have all the answers!

How Many Fish in a 5-Gallon Tank?

It’s hard to give a straightforward answer to this question. There are many things that go into calculating the number of fish that can go into a tank. 

However, a general rule is that you can keep 2 – 4 fish in a 5-gallon tank. 

Some experts say that you can keep an inch of fish per gallon of water. However, this isn’t always the case, especially if you plan on keeping larger species. 

Even if you decide to keep smaller species, there are many other things you need to consider. This includes:

• The temperament of the fish. Territorial fish, such as bettas, won’t like sharing a much larger space, let alone 5-gallons!
• Fish’s social needs. Some fish love living in large groups. If you keep a small group of them, even in a small tank, you might stress them out. 
• Shoaling behavior. The reason why some fish love living in larger groups is due to shoaling behavior. They want to swim in large groups and require lots of space.

So, how many fish in a 5-gallon tank? Let’s get even deeper!

Tank Density Explained

An important thing to consider when determining the number of fish that can live in a 5-gallon tank is tank density. 

Tank density is how many fish you can keep per tank size or per water gallon. It is one of the most important factors in fishkeeping. This is where the formula of one inch per gallon comes in handy.

In general, there are not many downsides to a small tank density, unless your fish species gets stressed out when found in a large open space.  

If the tank density is too large, however, your fish won’t be able to swim freely. They’ll be crowded, which can stress them out. 

Not just that, but tanks with large tank densities will become dirty much more quickly. This can lead to contamination and illness in fish.

Of course, as mentioned before, tank density isn’t the only factor that’s important when determining how many fish can fit a 5-gallon tank. Still, it is helpful to understand it and use it if you feel uncertain about whether you’re keeping too many fish in your aquarium.

Is a 5-Gallon Tank Big Enough? 

A 5-gallon tank is one of the most popular tank sizes, and it’s easy to see why. It’s compact and easy to fit into most spaces. Also, many people use it as a beginner’s tank, thinking they’ll have an easier time keeping it clean.

However, there isn’t an easy way to say whether a 5-gallon tank is too big or too small. This is too subjective for me to answer as it depends on many factors. 

For example, if you plan on keeping one betta, a 5-gallon tank is a perfect size! On the other hand, if you plan on keeping large fish such as dwarf gouramis or yoyo loaches, 5-gallons is less than a minimum tank size.

What Fish Thrive in a 5-Gallon Tank?

There are many fish you can keep in a 5-gallon tank. Most of these include peaceful fish that are fairly sturdy, not too sensitive to water temperature and hardiness changes. They won’t mind the limited space  that comes with such a small aquarium size.

Most dwarf shrimp species, such as blue jelly shrimp, as well as smaller snails, will also love a 5-gallon tank!

There are plenty of options for both novice and experienced fish keepers! 

Best Fish for a 5-Gallon Tank

1. Bettas

Betta splendens, also known as siamese fighting fish, are territorial fish that should always be kept in a species only tank. In fact, most people prefer having a single male due to its gorgeous colors and a long tail. 

I would never recommend having more than one male betta inside a tank. This is an aggressive and carnivorous species that will attack and kill most tankmates. However, there are many reports of a group of female bettas living comfortably in sororities. 

Fortunately, as bettas prefer living alone, they are great fish for a 5-gallon tank.

2. Chili Rasboras

Chili rasboras are a great option for small fish tanks! They move so fast it’s a delight to watch them. Also, due to their small size, they don’t require lots of space. In fact, they might be the best freshwater fish if you prefer a small size of tank. 

Just make sure to have good water quality! They are very sensitive to dirty water, so proper maintenance is the key. Don’t worry – you can clean your fish tank without actually removing the fish!

3. Celestial Pearl Danios

Celestial pearl danios is yet another common fish for keepers with small tanks. 

This is an easy-to-care-for species, but it prefers cooler water. It doesn’t have any challenging needs, and it is rather peaceful, so it can tolerate most tank mates. 

It’s important to note that you shouldn’t keep many males together, as they can become quite competitive.

4.  Dwarf Pufferfish

Dwarf puffer fish, also known as dwarf pea puffer, is the smallest fish from the pea puffer family – and it can easily be the cutest one!

Don’t let its adorable appearance fool you – this is an aggressive and territorial fish that has to be kept alone. Fortunately for you, this makes it an amazing choice for a 5-gallon tank!

Keep in mind, though, that this fish isn’t easy to take care of. As such, it isn’t a good choice for novice aquarium owners.

5. Killifish

Killifish is a large family of fish that consists of more than a 1000 species! While all have their own needs, most can be kept in a 5-gallon tank. 

You can keep these fish in groups with one female and several males, or you can keep them on their own. In general, I wouldn’t recommend keeping more than 3 killifish in one tank. Otherwise, they might feel crowded.

6. Molly

Mollies are some of the easiest fish to care for. They can adapt to almost anything and will thrive both in community tanks and on their own.

This adorable fish species comes in various colors, although the most famous ones are orange and black. 

While not the tiniest fish, they don’t mind crowded spaces and will live happily in a 5-gallon tank.

7. Scarlet Badis

Scarlet badis are beautiful, tiny fish that make an amazing addition to a small tank. They are amazing to watch and will easily become your favorite fish. 

When it comes to maintenance, they are not the easiest fish. However, with the right care, they will stand out in any aquarium!

8. White Cloud Mountain Minnows

White cloud mountain minnows live near the surface, so they can be great companions for crayfish and other bottom dwellers. Due to their small size, they’ll love a 5-gallon tank. 

The most challenging part is minnows’ trouble adapting to warm water. You must keep their water fairly cold, or they can become sick and eventually die.

9.  Pygmy Corydoras 

Corydoras are some of the most popular fish among aquarists. They are known as cleaners and make amazing beginner fish due to their hardiness.

Pygmy corydoras are the smallest corydora species that rarely grows to be larger than an inch. This makes them an amazing choice for small, 5-gallon tanks.

Due to their peaceful nature, they make great community fish, and you can keep them with most other species.

10. Harlequin Rasboras

Harlequin rasboras are unique-looking community fish that will love living in small tanks! In fact, as they can easily fall prey to larger fish, I wouldn’t risk keeping it in big tanks. 

This is a peaceful species that can adapt to most conditions. They don’t have high swimming levels and prefer spending their time in a shade, so make sure to give them plenty of hiding spots!

Other Animals that Thrive in a 5-Gallon Tank

Fish aren’t the only thing you can keep in your aquarium. There are plenty of other critters that can thrive in smaller places.

Here are some of them:

1. Red Cherry Shrimp  

If you know anything about me, you’ll know that I love shrimp, and this species is one of my favorites!

Red cherry shrimp is a peaceful dwarf shrimp species that can thrive in small tanks.

Due to their bright colors and small length, they don’t require a large amount of water nor a large tank. You can keep a fairly large colony in a 5-gallon tank without too much hassle.

Not just that, but you can keep it with most other dwarf shrimp types, such as bumble bee shrimp and the amano shrimp. They’ll even love live plants!

2. Ghost Shrimp 

Ghost shrimp are one of the easiest shrimps to take care of. They can survive in almost any condition – and this includes a smaller tank. 

These little critters are nearly transparent, so they might not be your first choice. However, if you combine them with brighter shrimp species, such as the blue tiger shrimp, they can look so much fun!

The only downside of keeping ghost shrimp is that they are rather challenging to breed in captivity.

3. Thai Micro Crabs

Thai micro crabs are my first choice for nano tanks, and they’ll thrive in 5-gallon tanks. In fact, you can keep up to 5-6 thai micro crabs in these aquariums, provided they have proper hiding spots.

They are fairly peaceful animals that can be a good source of food for many omnivorous or carnivorous fish, so choose their tankmates carefully. 

4. Dwarf Crayfish

Mexican dwarf crayfish look like mini lobsters, and you’ll certainly fall in love with them at the first sight!

They are peaceful crayfish that can coexist with many fish species – or you can keep them alone, in their own tank.

However, good advice is to never keep more than one dwarf crayfish in a 5-gallon tank. They require plenty of walking area, and most small tanks don’t have enough of that.

5. Mystery Snail

Mystery snails are probably the most common snail species in the fishkeeping hobby . Everyone has probably attempted to keep them at a certain point!

Due to their small size, they are a good choice for a smaller tank. 

My suggestion would be to keep a single snail with some fish species that can also live in a small aquarium. Otherwise, you’re risking becoming overrun with dozens of snail babies!

Fish to Avoid

Not all fish are suitable for small tanks, even though you might think otherwise.

Some fish I have seen people keep in 5-gallon tanks that I wouldn’t recommend include:

• Neon tetras.These fish are known for their schooling behavior.
• Guppies. Just like tetras, these fish have high schooling requirements.
• Most Gourami species. These beautiful fish grow too big for 5-gallon tanks!
• Goldfish. This famous species is rather dirty, so a small aquarium might not be a good option.
• Endler’s Livebearer. While recommended by many, I find this specie’s schooling behavior to be too much for a 5-gallon tank.

Are Small Tanks Better?

Small tanks don’t have a large surface, which means you can make the tank glass crystal clear much faster and you can replace the water rather quickly. Does this mean they are easier to maintain?

Believe it or not – the answer is no.

A small aquarium requires more maintenance than, for example, a 40-gallon breeder tank. Sure, you might complete the cleaning process much quicker, but there’s more to tank maintenance than that. 

Smaller tanks mean more sensitive water parameters. Water quality will become bad much quicker in a smaller tank compared to a larger one. Even the smallest change in any of the water parameters will have a much bigger impact on the water quality in the entire tank.

This means you’ll need to conduct thorough water testing more often in a 5-gallon tank than if you were to have a 20-gallon aquarium. Otherwise, you’re risking the health of the fish inhabiting it. 

Of course, I’m not trying to say that you shouldn’t have a small tank. However, you need to be aware of all the flaws so you can be certain you are ready for the obligations that go with a 5-gallon tank.

Final Word

Now you know that it isn’t easy to tell how many fish fit in a 5-gallon tank. While the question might seem easy, the answer is more challenging than it appears.

While many things determine just how many fish you can keep, it all comes down to the species you choose.

Some fish love to live in communities and don’t mind crowded spaces. Others prefer to be left alone and will hate any tank mates that disrupt their personal space.

Either way, there are plenty of choices for tanks of all sizes. Whichever you choose, I am certain you’ll provide your fish with the best possible conditions.