How Many Fish Can Be In A 5-Gallon Tank? Best Fish & Stocking Ideas

Safely stocking any nano tank (under 20 gallons) can have its challenges, but the resulting aquarium usually ends up looking like an underwater fairytale land. Well worth the research and effort! You may be wondering: how many fish can be in a 5-gallon tank?

The number of fish you can keep in a 5-gallon tank will ultimately depend on the species of fishes you place in it. We’ll get into all the details of an ideal nano 5-gallon tank setup in this article! 

First, let’s address a common misconception that often ends up deterring beginner aquarists from the fishkeeping hobby. Are smaller tanks easier to care for than larger setups?

No, unfortunately.

That’s not to say that a novice fishkeeper can’t maintain a thriving 5-gallon tank, but don’t be fooled into thinking a smaller aquarium requires less attention, and maintenance, than a 30-50-gallon tank.

See how you can set-up and aquascape a planted 5-gallon tank on a budget here:

How Many Fish Can You Safely Fit In A 5 Gallon Tank?

You may have read about the “one inch of fish per gallon of water” guideline that most online resources recommend when stocking a fish tank.

For larger-bodied fish, this rule of thumb can easily be dismissed and can even be dangerous to follow.

For smaller sized fish, this standard advice is somewhat helpful, but it doesn’t take into account a lot of factors, such as:

• a fish’s temperament: territorial fish won’t share their space even in a much larger tank, which makes them ideal for a nano aquarium setup;
• shoaling behavior: fish that need to swim in larger numbers just to feel safe, even if they’re in a single-species aquarium;
• a fish’s social needs: fish species that will be more stressed when alone than in a group, even if they don’t engage in schooling/shoaling behavior;

So, the answer to the question of how many fish you can keep in a 5-gallon tank will depend significantly on the type of fish you choose to stock it with.

There are plenty of options to choose from, but this article narrows it down to 9 species that will not only survive in a 5-gallon tank but will thrive in it!

What Can Live In A 5 Gallon Tank? 9 Best Aquatic Animals

1) Betta Fish

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Bettas are the perfect all-around fish for a 5-gallon nano tank. They’re territorial and enjoy having a space to claim as their own, without getting lonely or bored. Betta fish can live with other fish but should have a larger tank.

You’ll need to make sure there are plenty of live plants (less likely to hurt their long-flowing fins than fake plants) and lots of decorations for your betta fish to explore.

You should only keep one betta in a 5-gallon tank, as pairing two male bettas will inevitably lead to constant fighting, while a male-female pair of bettas will lead to stressful harassment for the female with not enough room to escape her partner’s insistent pursuit for mating.

2) Endler’s Livebearer

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Endler’s livebearers have the advantage of being much smaller than their Guppy relatives, allowing them to live comfortably in groups of 6 in a 5-gallon tank.

They come in brightly toned colors and will make the little underwater ecosystem in your home look animated and exciting.

Watch closely for new inhabitants, as they are prolific breeders and can overpopulate a nano tank if left to their own devices.

3) Celestial Pearl Danio

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Celestial pearl danios (see our care guide by clicking here) are a favorite choice for 5-gallon tanks because they are hardy fish, with minimal tank requirements. They’re considered coldwater fish, so you can get away with an unheated tank setup.

They’re also called “galaxy rasboras”, so it’s obvious they’re mesmerizing to look at! They put on quite a show when swimming, although they don’t engage in typical shoaling behavior. 

Male danios can get rough when competing for a female’s attention, so if you’re stoking a 5-gallon tank with six celestial pearl danios, make sure the female-to-male ratio falls in the female’s favor (4:2 is ideal).

Also keep the water temperature on the cool side since celestial pearl danios thrive in highland regions.

4) Least Killifish

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You can keep a female-male pair of least killifish in a 5-gallon tank. You’ll see them swim together all the time, as an inseparable couple.

They can grow up to 0.8-2 inches long at most, but they’re very active swimmers, so 5 gallons is the minimum tank size they require. Along with some plants and a few décor elements for entertainment, there’s not much else they need to be content.

Be sure to only get one male when keeping two least killifish. And look out for any fry, as the lovely couple might increase the fish population in your aquarium.

5) Sparkling Gourami

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Sparkling gouramis are a small variety of gourami fish that you can safely stock a 5-gallon tank with. They are also called “croaking gouramis” as they make an audible sound using their pectoral fins!

The males of this species will get aggressive when sharing a small space with another male, and they can also harass a female insistently if you were to keep a couple in your aquarium.

The best option is to keep one male and two female sparkling gouramis, as the male’s attention will be divided, making for a more peaceful atmosphere in your nano tank.

They do best in a heavily planted aquarium, and adding a light fixture will amplify their shimmer as they explore their surroundings.

6) Pea Puffer

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Dwarf pufferfish are miniature-sized feisty carnivores that can mislead you into thinking you can keep them in larger groups in a nano tank.

The truth is you should only keep a pair of pea puffers in a 5-gallon tank, as their temperaments are bigger than their 1.4-inch size. Pea puffers are territorial and chase each other around all the time.

They can also be hard to pair with other tank mates in such a small space, as they will nip, explore and satisfy their curiosity for other fish with their teeth (yikes!). Good thing they’re cute as can be and will put on a show as they go about their business!

7) Thai micro crabs

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Going into invertebrate territory, Thai micro crabs make excellent nano tank inhabitants, especially if keeping just a couple of fish in an aquarium makes it look less lively than you would like it to be.

You can keep up to 6 Thai micro crabs in a 5-gallon tank. They will peacefully share this small setup with other tank mates if given plenty of low hiding spots and refuge areas (bushy plants).

Choose tank mates with care. Small invertebrates are a favored source of food for almost any fish species.

8) Red Cherry Shrimp

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Cherry shrimp (see our care guide by clicking here) are some of the hardiest invertebrates you can keep in a nano tank. They add a pop of color and will spend most of their time cleaning up after their other tank mates, eating sunken leftover food, algae, and plant matter.

You can keep up to 10 red cherry shrimp in a 5-gallon tank as they clean up the water in your tank more than they dirty-it up. We have an entire post dedicated to how many cherry shrimp you can keep per gallon – check it out!

Make sure you check for compatibility when having them share a nano tank, as they can be viewed as snacks by some fish.

Cherry shrimp also breed with ease and make good pets to share with friends that have fish tanks!

9) Mexican Dwarf Crayfish

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 Mexican dwarf crayfish are the smallest variety of dwarf crayfish, and you can keep one in a 5-gallon tank along with other peaceful tank mates.

It’s like having a mini-lobster in your nano tank! This 2-inch invertebrate will need a number of refuge areas to feel safe, even in a small tank, because they will molt regularly.

Popular Stocking Combos For A 5-Gallon Tank

It’s important for all species in a tank to have good compatibility. Generally, you should aim to include species that don’t bother one another.

Here are a few combinations you should consider:

Combo #1

• 1 Betta;
• 2 Cherry Shrimp.

Combo #2

• 5 Cherry Shrimp;
• 2 Thai Micro Crabs.

Combo #3

• 4 Celestial Pearl Danios (3 females, 1 male);
• 2 Cherry Shrimp.

Check out some other notable combinations in the short video below:

Fish You Shouldn’t Keep In A 5 Gallon Tank

When it comes to keeping certain fish species in a nano tank, opinions vary greatly among experienced fishkeepers, depending on their past experiences. You have to remember that all fish are individuals at the end of the day, so you’ll rarely get the same outcome when pairing them with tank mates.

Keeping a betta fish in a 5-gallon tank with a few invertebrates sounds like the easiest fish tank stocking combo until you find a betta that just has a taste for eating shrimp.

This is the reason why although some of the species listed below might be recommended for stocking a nano tank (<20 gallons), they might not be an option for a 5-gallon tank.

Here are some of the fish species you shouldn’t keep in a 5-gallon tank:

• Messy fish such as goldfish

Apart from being social creatures that like company, goldish are generally considered to be messy aquarium fish. They produce a lot of waste, and they dig at the substrate polluting the water inside a tank even further. Goldfish also grow anywhere from 8 to 12 inches long. A biological overload for a 5-gallon tank!

• Sensitive fish such as pygmy catfish

Fish that don’t do well in a tank that’s susceptible to sudden changes in water parameters shouldn’t be kept in a 5-gallon tank.

The water chemistry inside a nano tank can easily fall off-balance and wipe out a population of pygmy catfish, which are considered a reliable cleaning crew for large community tanks.

• Active schooling/shoaling fish such as neon tetras and most guppies

Although guppies and neon tetras have the size that would make them fit inside a 5-gallon tank, they would be far from thriving and practically just surviving.

They need to live in sizable groups, and the limited space won’t allow them to swim freely and be as active as they’re meant to be. Stress alone will kill them!

• Territorial fish such as angelfish

Angelfish will not only grow too big to fit inside a 5-gallon tank, but even if kept as juveniles in a nano tank, they won’t do well. They will nip at their tank mates and fight insistently for territory, being under constant stress. A big NO!

• Large fish such as cichlids

Oscar fish, and similarly sized cichlids, will quickly outgrow a 5-gallon tank and will even have a hard time in it as juveniles since they’re very active and territorial.

Best Live Plants For A 5 Gallon Tank

Adding live plants, or even better, setting up a heavily planted 5-gallon tank, is the best strategy for keeping the water quality inside your nano tank at a comfortable level for its inhabitants.

Plants also make excellent resting and hiding areas for shy critters while also giving fish exploring opportunities. For a 5-gallon tank, you should choose live aquatic plants that are less demanding.

A few plants that don’t need fertilizers, specialty lights, or any expert-level maintenance are:

• Java Fern;
• Brazilian Micro Sword;
• Anubias;
• Java Moss;
• Marimo Moss Balls.

Even a few live plants can make a big difference in how stable the water parameters in a 5-gallon tank will be, so don’t be intimidated if you’re a beginner in setting up planted aquariums. These plants are as low-maintenance as they come!

5 Gallon Fish Tank Setup

A 5-gallon tank is an ideal choice if you have limited space in your home and/or if you want to start small budget-wise. Going for an even smaller tank capacity isn’t recommended, as even the tiniest aquarium critters need room to swim and explore.

Not giving your fish enough space to swim, explore, or even get away from each other at times is not the only risk you’re taking if you were to add too many fish in a 5-gallon tank.

The waste your fish inevitably create can trigger a biological imbalance and turn the water inside your nano tank toxic. The good bacteria inside your tank can only process and convert so much ammonia into non-toxic nitrates.

As counterintuitive as it sounds, nano tanks are actually higher maintenance than larger tanks.

An established 5-gallon tank will require you to stay on top of a strict cleaning schedule to keep the water crystal-clear and your fish healthy:

• Weekly 50% water changes (biweekly if stocked to maximum capacity);
• Clean filter media weekly;
• Trim plants and remove dead plant matter often;
• Siphon the gravel weekly.

The steps in this maintenance routine should be done on alternating days of the week to avoid removing too much of the nitrifying bacteria inside your tank.

The limited space inside a 5-gallon tank can make the process of setting it up feel like a perpetual Tetris game. Fitting enough decorations/live plants inside while still leaving open space for free swimming definitely requires some creativity on your part.

Gear You Need For A 5 Gallon Tank Setup

You can set up a 5-gallon tank with as few as four gear elements in total if you’re going for a low-tech system that can easily fit on a desk in your office or in any room of your home.

5-gallon tank

Get a 5-gallon nano tank with a built-in filter if you choose to stock your tank to its maximum capacity or if you just want to have an easier time keeping water quality high inside the aquarium.

Bacteria starter

A bacteria starter for fishless tank cycling will give you a head start in setting up a 5-gallon tank that has its own biological filtration already running (good bacteria!) even before you stock it with fish.

Follow the directions on the bottle to avoid overdosing. For a 5-gallon tank: add 20 drops daily for the first two weeks of use during the initial set up, followed by 10 drops per week.

Establishing a culture of nitrifying bacteria will prevent the water from turning toxic due to leftover food decomposing or the sudden influx of fish waste when you start adding fish into your nano tank.

Heater

If you’re planning on making your 5-gallon tank a home for a betta fish, you’ll definitely need a heater.

The ideal water temperature inside a betta aquariumwater temperature inside a betta aquarium should be between 75-80°F. Cooler water will put your long-finned splendor at risk for disease and even stress it out to the point of death.

A 50-watt tank heater will do the job just fine in a nano tank!

Lights

Even low-maintenance live plants need light to grow, so if you’re going for a planted 5-gallon tank setup you’ll need some lights to keep the lawn green.

A clip-on LED light that you keep on a diurnal schedule (8-10 hours of light daily) will help your plants grow and allow your fish to self-regulate stress levels (too much or no light at all can have a negative impact on your fish).

Conclusion

A 5-gallon tank can be a challenge to maintain, as it requires a lot more hands-on care than a larger aquarium. On the other hand, it’s much easier to set up and stock.

You are limited in how many fish you can keep in a 5-gallon tank and which species you can choose from, but on the other hand, decorating and planting a nano tank leaves room for unlimited opportunities at a fraction of the cost of decorating a 30-50-gallon tank.

Recommended Reading:

• How To Plant Carpet Seeds In An Aquarium – The Ultimate Guide
• How Many Cherry Shrimp Per Gallon?
• Keeping Your Fish Tank Clean – Supplies & Methods