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How Many Fish in a 5 Gallon Tank? (with 10 Types of Fish)

how many fish in a 5 gallon tank

To calculate the right number of fish per gallon, you need to consider fish size, swimming space, and surface area.

So, how many fish in a 5 gallon tank?

If no fish is bigger than 1 inch, you can keep roughly 2-6 fish in a 5-gallon tank. Most smaller fish breeds would be subject to the one-inch fish per gallon limit.

A 5-gallon tank should not be used for fish that can grow into much larger sizes. There won’t be enough space for them to move around. It’s best to keep only male ones for those that reproduce fast.

For wide-bodied fish, each 1-inch fish should occupy twenty inches of the tank’s surface area. Surface area is where gas exchange takes place (oxygen in and carbon dioxide out).

Table of Contents

General Rule for Stocking a Fish Tank


Aside from figuring out how many fish can go in a 5 gallon tank, it would help if you also considered everything else you’re going to include in your tank. Live plants, gravel, filters, lighting, and ornaments also take space.

When it comes to the number of fish, your tank may hold one inch of fish for every twelve square inches of surface area, according to the water surface area rule. Using the surface area rule, you can calculate by multiplying the tank’s width by its length.

Ideal Fish And Critters For A 5 Gallon Tank

Choosing the right types of fish is essential for nano tanks. Which fish can be in a 5 gallon tank? Here are some:

1. Molly Fish


Size 3-4.5 inches
Care Level Easy
Diet Omnivorous
Temperature 75-80°F
Temperament Easygoing
Number of Mollies you can keep in a 3-gallon tank 2-3

A freshwater fish from Central America, molly is a flat-bodied fish with small fins. They come in different colors such as yellow, white, orange, and black.

Mollies are peaceful and sociable. You can keep them in groups of 4, just always keep in mind not to take up much of their space with stuff. Overcrowding can make them pretty aggressive.

2. Tetras


Size 1.5-2 inches
Care Level Easy
Diet Omnivorous
Temperature 72-80°F
Temperament Calm/Semi-aggressive
Number of Tetras you can keep in a 3-gallon tank 3-5

Tetras are perfect for both new and experienced hobbyists since they are peaceful, colorful fish. Red eye, black skirt, serpae, and bloodfin tetras are great for beginners, but neon, glowlight, and lemon tetras are also great candidates.

Most tetras are calm and mix well with other fish of the same size. However, breeds like Serpae tetras can occasionally be aggressive, especially when housed in small numbers.

3. Cherry Shrimp


Size 0.75-1.5 inches
Care Level Easy
Diet Omnivorous
Temperature 65-78°F
Temperament Calm
Number of Cherry Shrimp you can keep in a 3-gallon tank 5-10

Available in various red hues, cherry shrimp are widely known for eating algae and keeping fish tanks clean. They are content spending some time alone while consuming waste. They don’t produce a lot of bio load, so they are ideal for nano tanks.

You can house one or two red cherry shrimp with a betta fish, but you need to give them enough plants to hide in.

4. Ghost Shrimp


Size 1-2 inches
Care Level Easy
Diet Omnivorous
Temperature 70-82°F
Temperament Calm
Number of Glass Shrimp you can keep in a 3-gallon tank 10

Also known as glass shrimp, ghost shrimp are unique because their bodies are almost entirely transparent! This allows them to camouflage in any environment.

Ghost shrimps are also great companions for betta fish. With their clear form, they can’t overshadow your betta’s bright colors.

5. Betta Fish


Size 2.25 inches
Care Level Easy
Diet Carnivorous
Temperature 75-80°F
Temperament Semi-aggressive
Number of Bettas you can keep in a 3-gallon tank 1-2

Among the list of fish that can live in a 5 gallon tank, betta fish are the most striking. Their vivid colors can liven up any aquarium and their appearance makes them wonderful to watch. They have flowing tails that look majestic when they swim!

Betta fish are quite low maintenance so they are easy to take care of. You can feed them a variety of food, but it’s best to give them protein-rich pellets or frozen bloodworms.

You must house only one betta fish per 5 gallon tank–they can be highly territorial and fight each other off(especially males). However, you may keep them with adult cherry shrimps or small calm fishes.

6. Chili Rasbora


Size 0.7 inches
Care Level Easy
Diet Omnivorous
Temperature 68-82°F
Temperament Calm
Number of Chili Rasboras you can keep in a 3-gallon tank 5-6

Chili Rasboras are cute tiny fishes that can swim in a flash. They are one of the coolest fish for a 5 gallon tank because of their bright red hues and fascinating movements.

Rasboras is a great type of fish to keep in a 5 gallon tank with a betta. Their timid and laid-back personality prevents them from engaging in fights with other fish.

7. Guppies


Size 1.2-2 inches
Care Level Easy
Diet Omnivorous
Temperature 72-82°F
Temperament Easygoing
Number of Guppies you can keep in a 3-gallon tank 3-5

Loved by many fish owners, guppies are the easiest to take care of. They are not aggressive–they are just quick, playful little pets!

Guppies and snails are among the most ideal 5 gallon tank fish combinations. They get along well, plus, snails will clean up guppies’ food leftovers.

8. Nerite Snail


Size 1-1.5 inches
Care Level Easy
Diet Herbivorous
Temperature 72-82°F
Temperament Calm
Number of Nerite Snail you can keep in a 3-gallon tank 1-2

Aside from being well-known for their ability to clean aquariums, nerite snails are among the most gorgeous and unique freshwater snail species. Nerite snails usually have striking stripes or barred patterns on their shells, which inspired people to call them “zebra” or “tiger”.

Nerite snails are remarkably calm—you can keep them with various fish species. What’s more, they can only reproduce in saltwater meaning there is very little chance that they will overcrowd a freshwater tank.

9. White Cloud Mountain Minnow


Size 1.5 inches
Care Level Easy
Diet Omnivorous
Temperature 64-72°F
Temperament Easygoing
Number of White Cloud Mountain Minnows you can keep in a 3-gallon tank 5

These fish have a traditional, streamlined body. They are wonderful additions to 5-gallon tanks not just for their adorable size and look: they also inhabit the center of your tank so they don’t need hideouts.

White Cloud Mountain Minnows like to explore new places. They are very adventurous and quite curious about their environment!

10. Clown Killifish


Size 1.2-1.4 inches
Care Level Easy to Moderate
Diet Carnivorous
Temperature 68-79°F
Temperament Calm
Number of Clown Killifish you can keep in a 3-gallon tank 2-3

Clown Killifish are so small that three of them can be housed together in a 5-gallon aquarium. They are long and rocket-shaped—their body is covered in a variety of vibrant hues (red, blue, black and yellow) and have striped patterns. Males have more vivid colors than females.

Plants and other vegetation are often of no interest to clown killifish. They prefer to stay at the surface where they can catch insects and other creatures to eat.

Tips on Calculating Tank Density


Always use net gallons when applying the 1-inch rule and consider a fish’s form and mature size. Moreover, the surface area rule works better for aquariums of non-standard size. Either way, you need to do your research first.

Remember that going under the limit rather than over is a must. This is also true for schooling fish–never keep more than what’s recommended.

Tips on Setting Up a 5 Gallon Tank


After getting your nano tank, you need to check it for any dirt or dust–even a brand-new one needs a wipe. Used tanks can be cleaned with vinegar and warm water.

Fish tanks must be placed away from natural light sources to prevent algae growth. They must also be kept far from any heat sources. When choosing the right location, don’t forget that your tank will be heavier once filled with water.

Cycle your tank before adding fish to it. Be careful: you can easily lose control of water chemistry in a small tank. Cycling involves allowing beneficial bacteria buildup to convert toxic ammonia and nitrates (from waste); it usually takes 4-6 weeks to complete.

For cleaning and maintenance, make sure the equipment is running well, change the water at least once a week, and cycle at regular intervals. Maintain the growth of good bacteria to keep your pets safe.

Frequently Asked Questions

Is A 5 Gallon Tank Big Enough For 2 Fish?

Depending on the breed, mature size, and needs of a fish, a 5-gallon tank can house two compatible fish that won’t grow more than 2 inches. Make sure that they have enough space to move around freely.

Why Should You Use A 5 Gallon Tank?

5-gallon tanks are a great choice for your first aquarium since they are practical and compact. You can place them in a small apartment or any area without much space for larger aquariums. Not to mention, they are cute! Children and pets will love them.

Which Fish Breeds Are Not Suitable For A 5 Gallon Tank?

Any fish that grows beyond 2 inches is not ideal for a 5-gallon tank. Corydoras or Cory fish can grow up to 4 inches in size. Large Snails are also not best for a nano tank. They can grow too large and produce a lot of waste.

Goldfish in a 5 gallon tank is not a good idea as well–they are pretty, but they generate a ton of waste too. A small space is unhealthy for them, and the water can easily get dirty.


How many fish in a 5 gallon tank? Well, you should consider fish size, swimming space, and surface area. If none of the fish are larger than 1 inch, you can keep around 2-6 of them. Fish that can grow much larger could be better and wide-bodied ones should occupy only twenty inches of the tank’s surface area.

The best fish and critters for a 5 gallon tank are mollies, tetras, cherry shrimp, ghost shrimp, betta fish, chili rasboras, guppies, nerite snails, white cloud mountain minnows, and clown killifish. Nerite snails get along well with others, while bettas are better off with cherry shrimps.

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