Best Fish for a 5 Gallon Tank – Perfectly Suited to Small Environments

Setting up a 5-gallon tank can be difficult as it’s not a big space, many fish need a far larger environment, and there’s somewhat confusing information available both locally and via the internet.

First of all, you need to know which fish are best suited to 5-gallons; how many can fit together and the different species that can live in harmony.

Close up of a beautifully colored small fish in a planted tank, background blurred

The 5-gallon tank is a great size for beginners, but it’s also very easy to overstock if you don’t have the correct information.

Ideally, it’s the smallest size tank for keeping fish that we recommend on this site, which does restrict your options somewhat.

With that in mind, we have compiled a list of seven recommendations for the best fish for a 5 gallon tank or aquarium, and after the list we cover the things you need to consider before you can head out to buy any.

The Size of The Fish is Super Important

When considering fish for your 5-gallon tank, the first thing to think about is the size of your fish. Just because a fish can fit in a 5-gallon tank, it doesn’t necessarily mean it will suit their individual needs.

For instance, a common goldfish requires a minimum of 40 gallons, and a fancy goldfish requires 30 gallons. A 5 gallon tank is quite simply too small for many species of fish.


You also need to consider the social habits of fish. Certain schooling fish, for example, may be too timid if not kept in large numbers, they just aren’t meant to be alone.

So although a single fish may seem OK, you aren’t allowing the fish to exhibit natural behaviors. But if you did buy many to allow them to school, it can take the bio-load over what such a small tank can handle.

So if you do decide to stock schooling fish in a 5-gallon tank, you need to be aware of certain restrictions and be prepared to upgrade in the future.

How Many of a Particular Species?

When deciding how many fish you can have in your tank, you need to consider ‘fully grown fish,’ not the current size – unless you are prepared to upgrade your tank size accordingly

‘Fish load,’ takes into consideration the burden fish place on the aquarium’s ecosystem. The waste produced by fish, the amount of oxygen in the water and the number of contents all contribute to the tank’s equilibrium.

The smaller the tank size, the more you need to consider keeping an ecological balance in your tank and the less fish you can have.

To determine how many fish to keep in your 5-gallon tank you can apply the following two rules of thumb:

One Inch of Fish Per Gallon Rule

A commonly used rule for determining how many fish to keep in a tank is by calculating one inch of fish per gallon of water.

This rule should only be applied as an approximate indication, as there are plenty of factors to skew the results. You need to factor in the types of fish you wish to keep, your lighting system, live plants, and filtration systems.

Fuller bodied fish create more waste than thin fish measuring the same length and will need more water. Active swimmers and schooling fish require more room to swim than bottom feeders.

Remember, you need to factor in the adult size of your fish, not the current size. You will need to do a little research surrounding the fish you like to establish its ‘fully grown size.’

When considering your 5-gallon tank, subtract the contents such as plant life and the substrate when determining how much actual water your tank will hold.

Use the one inch of fish per gallon rule with the above factors in mind to avoid overstocking your aquarium.


The Surface Area Rule

The more water there is in contact with air at the top of a tank, the more oxygen will be available, which allows for a higher amount of fish.

What this means, is that the surface area of the water directly correlates with the number of fish you can keep in a tank.

Portrait-styled, 5-gallon tanks may hold the same amount of water as its landscaped counterparts, but their surface areas are considerably different. When applying this rule to determine the number of fish to keep, the differences in shape is considered.

It works by multiplying the length by the width of the tank to determine the surface area. Following this rule, you can fill your tank with one inch of fish for every twelve square inches of the surface area.

Where this rule falls down, is in its inability to allow for full-bodied fish. It makes the presumption that all fish are slender-bodied and with that in mind you need to use this rule as an estimate only.

Note: If you’re yet to buy your tank, we have a buying guide and list of some of the best 5 gallon tanks to be found in 2018 that might interest you.

Can You Mix Different Species?

Some fish can cohabit together in perfect harmony, whereas many cannot. It is essential to refer to the rules surrounding the number of fish suitable for a 5-gallon tank and then look at which of them can have a tankmate.

For a full list of compatible fish, please see the freshwater fish compatibility chart and the marine fish compatibility chart.

Our Recommendations for the Best Fish for a 5 Gallon Tank

We’ve selected and discuss a few favorite species of fish, particularly suited to the 5 gallon environment, and have mixed in some shrimp and crabs too, because there’s more to aquatic life than juts fish!

Hopefully you’ll find something below that interests you? And we’ve included basic care requirements and more to help you in your decision making.

Siamese Fighting Fish (Betta Splendens)

A red, white and blue betta fish, isolated against a blurred planted background

  • Origin: Thailand and Cambodia
  • Maximum size: 2.4 inches
  • PH of water required: 6.8-7.5
  • Diet: A carnivorous diet of high-quality Betta pellets, mosquito larvae, bloodworms, brine shrimp and small live shrimp.

Bettas are a stunning fish that come in a variety of colors and fin shapes, making them a top favorite with fish-keepers around the world.

This beautifully colored tropical fish requires a heated, filtered, landscaped shaped tank with a lid. It should not be in anything less than 5-gallons and needs to be able to breathe air at the surface of the aquarium.

Bettas enjoy a calm, tranquil aquarium environment with plants and relaxed tankmates.

Standard aquarium gravel is ideal for Bettas and is a lot easier to clean. In saying that, larger pebbles are also suitable.

The male is the most commonly found in pet stores – recognizable by their large, colorful, flowing fin. To intimidate or impress, the male Betta will flare their fins out. The female Betta has less colorful and shorter fins and can sometimes be mistaken for the male short-finned species.

They have enormous appetites and will beg for food; however, it is important not to overfeed them, and you can even get away with missing a day’s worth of food occasionally.

Bettas need plenty of room in their tank to thrive, and it’s not recommended you keep two males in an aquarium together. Most experts do not recommend keeping more than one Betta in a 5-gallon tank.

Bettas are active and curious fish, with outgoing personalities towards both their owners and tankmates (providing they are in big enough tank). If your Betta is colorful and actively patrolling the tank, begging for food and excited by your presence in the room – know you have a healthy Betta.

Least Killifish (Heterandria Formosa)

Close up of a Least Killifish
© Vladimir Wrangel / Adobe Stock
  • Origin: North America
  • Maximum size: Males 0.8 inches Females 1.2 inches
  • PH of water required: 6.5-8
  • Diet: Ground flakes, micro pellets, live foods (brine shrimp and micro worms) and frozen foods (baby brine shrimp and copepods)

As the smallest fish in North America, this peace-loving species is olive in color with a dark stripe which runs sideways across its body. The Least Killifish is a resilient fish but should be kept with lots of plant life with a mild filtration system to ensure the water flow is low.

As omnivores, Killifish will eat most food sources in the aquarium. They will need some plant matter as well as animal sources (both live and frozen) such as brine shrimp. To keep your Least Killifish in peak health with full-color capacity its recommended you feed them a varied diet of both invertebrates and vegetation.

Although peaceful, they aren’t considered as a community fish. Due to their minute size, they can be easily eaten by other community fish, making them suited to a group of other Least Killifish.

In a 5-gallon tank, you could stock two Least Killifish; however, this is only an estimate and an extremely rough guide if using only the 1 inch of fish per gallon rule. If you have an unusually shaped tank, you should use the surface area rule.

Dwarf Puffer (Carinotetraodon Travancoricus)

An extreme clos eup a dwarf puffer fish against some aquarium rock
By Till Kresslein – Own work, CC BY-SA 3.0, Link
  • Origin: Southwest India
  • Maximum size: 1 inch
  • PH of water required: 6.5-7.8
  • Diet: Carnivorous; snails, mosquito larvae, bloodworms, tubifex, blackworms

Known as the smallest puffer species (sometimes referred as pea puffers), the majority of these tiny fish will not grow to be more than an inch in size. They are very territorial and in large tanks need a lot of places to explore and hide. They are very active and will fight each other in large aquariums if there’s enough to distract them, in the way of plants and decorations.

The color on the dwarf puffer is determined by their mood, ranging from green to brown with darker spots. After they have fed their belly is white to yellow and smooth. If you notice its belly looking bumpy at any stage, it may be an indication your fish has parasites.

The dwarf puffer is not considered suitable for a community tank as they tend to nip and chase their tankmates. They are best kept on their own although, peaceful shrimp such as the cherry shrimp have shown to be successful tankmates due to the adult size being too big for the dwarf puffers to eat.


The dwarf puffer will eat snails as well as a combination of fresh and frozen foods such as bloodworms, blackworms and mosquito larvae. With frozen products ensure you soak them in water before feeding to avoid overfeeding your fish. The dwarf puffer generally won’t eat flake food or pellets.

The tank needs to be fully cycled to remove all traces of nitrates or ammonia before introducing your dwarf puffer. Easy-to-grow live plants such as java fern and java moss and are a great addition to your puffer’s aquarium. They are generally suited to any substrate although sand appears to the most popular amongst dwarf puffer enthusiasts.

The dwarf puffer is a fascinating fish to watch due to their active, intelligent personalities. Keep in mind that they are ideally suited on their own in 5-gallon tank and refer to the one-inch rule as an estimate only. Should you decide to stock cherry shrimp with your dwarf puffer, a wide tank is recommended.

Dwarf Crayfish (Cambarellus Genus)

Close up of an orange dwarf crayfish in a gravel bottomed tank

  • Origin: Mexico and Southern parts of America
  • Maximum size: 2 inches
  • PH of water required: 6.5-8
  • Diet: Omnivores; pellets, bloodworms, peas and black mosquito larvae

The dwarf crayfish is peaceful and suited to many community tanks. With the look of a miniature lobster, dwarf crayfish have a few varieties and range from brown-grey coloring with stripes darker than their overall color, to bright orange – the most commonly kept due to their brighter color.

The dwarf crayfish does not require heavy filtration, with only needing a small filter to remove particles and cycle the tank. It’s imperative never to stock an uncycled tank as they respond very severely to ammonia and nitrates. They also do very well in small tanks – especially if there are many places to hide – and those containing plants, rocks, and wood.

These bottom feeders will eat most of anything including frozen bloodworms and mosquito larvae, algae pellets and peas. Dwarf crayfish have a curious personality, often being seen attempting to approach one another only to jump back to prevent getting too close. They are confidently territorial despite their tiny size.

They are peaceful enough to share a tank with a variety of other species and generally only kill weak, tiny fish. Another vertebrate such as baby and bamboo shrimp or small snails may be vulnerable to dwarf crayfish damage but generally speaking, they mostly do no harm – living in unity with the majority of community tanks not stocked with big, hungry fish.

Depending on the size you could stock two of these in a rectangular, 5-gallon tank. Regarding sharing with other species, you would need to refer to the fish per gallon rule or surface area rules depending on the shape of your tank.

Cherry Shrimp (Neocaridina Davidi)

Bright red cherry shrimp resting on sand

  • Origin: Taiwan, China & various parts of Asia
  • Maximum size: 1 inch
  • PH of water required: 6.5-8
  • Diet: Omnivorous; eating specific shrimp food, algae pellets, and blanched vegetables

The cherry shrimp is a type of dwarf shrimp loved by many fish keepers for how easy they are to care for and their striking bright colors.

The female cherry shrimp grows no bigger than an inch, with the male variety usually smaller. Female cherry shrimps also sport a brighter shade of red than their male counterparts.

Cherry shrimp are relatively easy to take care of. Ideally, they should live in groups of at least five and can exist in a vast range of environments.

Avoid exposing the cherry shrimp to any medications containing copper or an uncycled tank as they’re hypersensitive to nitrate and ammonia. Ensure you change the water in the tank every week and pair the new water to the previous in both water and temperature values.


There is no issue keeping cherry shrimp with larger fish provided they have lots of hiding spots and other plant life. Regardless, you could still be taking a risk stocking them with carnivorous fish such as Bettas.

They are excellent little scavengers and will clean up all the leftover food flakes from their tank mates or anything they find in the plants. If you are only stocking cherry shrimp in your 5-gallon tank do not overfeed them; a small amount of food each day will suffice and ensure you remove any excess bits they haven’t consumed within three to four hours. Food that has been left in the tank for long periods of time can create dangerous levels of ammonia.

Cherry shrimp are very serene spending the majority of their time looking for food. In a 5-gallon, single species tank, you could ideally stock five cherry shrimp, comfortably although people do stock more than that. If you want to stock a community tank, you will need to you refer to the stocking rules as a rough guide.

Thai Micro Crab (Limnopilos Naiyanetri)

Front view shot of a Thai micro-crab, standing on rear legs with front legs in the air
By Sean Murray from Edinburgh, Scotland (Limnopilos naiyanetri 1) [CC BY-SA 2.0 ], via Wikimedia Commons
  • Origin: Thailand
  • Maximum size: 0.04 inches
  • PH of water required: 6.5-7
  • Diet: Omnivorous; frozen mosquito larvae, plant-based shrimp foods, pellets.

These tiny little crabs grow no larger than an inch making them ideal occupants of a calm aquarium system. Brownish-grey in color, the Thai micro crab, has thin, long legs and small bristles protect every part of its body – used to catch food particles.

They enjoy a fully cycled, filtered system with a lot of dense plant life and decorations in their tank. This enables them to be able to hide in various places due to their shy personalities. It would be a good idea to add a few floating plant roots and driftwood to your aquarium to replicate their natural inhabitant.

Thai crabs cannot defend themselves, therefore when stocking a community tank, you should only keep them in peaceful communities. Ideally, you should house them in groups of five with other small invertebrates and calm fish. Cherry shrimp or small schooling fish can make ideal tank mates for the Thai micro crab. They eat an omnivorous diet and can live off the micro-organisms floating in their tank.

Due to the shyness of their nature, the Thai micro crab spends most of its time hiding in plants and will generally only surface in the presence of food. They do tend to escape their tanks, therefore keep a lid on it and don’t have any large holes used for chords or other equipment.

White Cloud Mountain Minnow (Tanichthys Albonubes)

A white cloud mountain willow isolated on dull bluey-green background

  • Origin: China
  • Maximum size: 1 ½ inches
  • PH of water required: 6-7
  • Diet: Omnivorous; flakes, pellets and live foods

The White Cloud minnow is a metallic greenish color with a red caudal and fin. They usually grow to be around 1 ½ inches long, with the male sporting a more, slender build and brighter shade of color than the female. They can usually be found in the mid to top area of the aquarium.

To thrive these fish cannot be kept singly, or they lose their coloring and spend most of their time in hiding. They are very serene and do well with other small calm fish.


Apply the surface area rule as a rough guide, if you have an unusually shaped tank and wish to stock a community aquarium. This species of fish is ideal for a beginner fish keeper as it does well in most environments. In saying that, it is not suited to heat, with 18-20 C being the preferred temperature. The substrate should be sand with dark pebbles, with a few plants, rocks and driftwood.

White Cloud Mountain Minnows eat a variety of food, often feeding on small invertebrates. They are happy to eat flakes, crisps, bloodworms, brine shrimp, daphnia and freeze-dried foods. The male of the species are known to chase the female with so much enthusiasm causing the female to jump out of the tank, so always use a cover on your aquarium.

Happy fish keeping!

B Hamilton

Hey there! I'm Brian, a lifelong enthusiast and fish keeper with a wealth of knowledge and experience on freshwater aquariums, that I love to share on this site. If you have any questions or need any help, please do ask in the comments section below, I'd love to hear from you and will help where I can.

4 thoughts on “Best Fish for a 5 Gallon Tank – Perfectly Suited to Small Environments”

  1. could you keep just male WCMM’s together, or just females to avoid jumping? also, how many could you have in a well planted five gallon with sand, rocks, and some spindly driftwood?

    • Hi Ashlyn,

      I like the line of thought! But to be honest, for the very fact they even can leap out of the tank I would also make sure there is a lid anyway, better safe than sorry!

      For the amount you can keep in the tank, please see the two rules at the top of the article, the one inch per gallon and surface area rules, which will allow you to calculate a healthy stocking level.

  2. Would a single Betta and a dwarf crayfish coexist in a 5.5-gallon tank?

    • Hi Alicia,

      Yes, should be fine, many people have had this combon in the past and 5.5 gallons should be big enough for them to co-exist. Just make sure to have a few small hiding places the crayfish can get into.

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