Stocking a 5 Gallon Tank. Fish and Inverts.

In the fishkeeping hobby, any tank that its capacity is less than 10 gallons (40 liters) is regarded as a nano tank, although this is subject to individual perspectives as some aquarists may even consider 10 and 15 gallons (60 liters) tanks as nano aquariums.

Stocking tanks under 10 gallons (40 liters) is difficult because of the limited options you are left with after considering many factors. On the bright side, few options do exist although it’s basically Bettas and invertebrates.

Small fish tanks such as the 30-gallon (12 liters) tank and 5-gallon (20 liters) tank can be purchased in fish stores at fair prices, but they have some limitations which will be discussed extensively in this article.

Apparently, a 5-gallon tank is capable of housing a single small fish and multiple invertebrate species. Because of its miniature size and capacity, it can be very easy to overstock. In its turn, that will only lead to more problems that you wouldn’t want the tank inhabitants to experience if longevity is what you desire.

This article will enlighten you on suitable fish species and inverts that can be kept in a 5-gallon fish tank as well as the best stocking ratio and proper maintenance guidelines.

Why Choose a 5 Gallon Tank? (Pros and Cons)

More often, individuals without prior experience in fishkeeping tend to choose a small/nano aquarium to start out with, and when they must have mastered the essentials, they will opt for mid or large tanks be it 20, 30, or 50 gallons depending on their preferences and budget.

Furthermore, another reason why people prefer a 5-gallon fish tank is because it allows for more flexibility. It is quite portable and easier to handle. Nano tanks can be easily mounted on a counter or cabinet, and of course, they cost a lot less than the larger tanks.

However, a 5-gallon fish tank has some serious cons too. Firstly, it places a limitation on the type and size of species and inverts that can be housed in it, this is a big problem although it is expected, you should know the compatible species that will fit into the small space it provides.

Secondly, maintenance is another issue for nano tanks because in practicality – the bigger the aquarium, the easier its maintenance will be.

The size of an aquarium directly affects the water chemistry: stability of water temperature, PH, hardness (GH and KH), and breakdown of metabolic wastes e.g. ammonia, nitrites, nitrate, and nitrogen cycle in general.

Additionally, if you overstock a smaller tank, it will require constant water changes more than tanks with larger capacities because the water quality will get ruined faster, hence making the environment unpleasant for the tank’s inhabitants.

Note: This can also cause problems for such animals as dwarf shrimp.

Lastly, it affects the quantity and behavior of fish. Larger tanks allow you to stock schooling fish which are best kept in groups of at least 5-6 specimens. For them to swim and shoal in the water column they will require enough volume of water and space.

However, smaller tanks have a restriction on the number of fish you can have, and species like Neon tetras, Pygmy Corydoras, or Zebra Danio cannot thrive in such conditions because they need to be kept in large numbers which a 5-gallon tank does not permit.

Also, territorial fish species will become overly aggressive when they are kept in tanks without plenty of space to roam, therefore they are not an option here.

tank easy to keep is not the size but Aquarius knowledge of what you can and cannot do. 

Pros of Small Tanks	Cons of Small Tanks
Low price	Unstable water parameters
Accessories cost (no need for powerful light, pump, heater)	Causes aggression
Weight (you can move it around if it is needed)	Increased stress
Less time for maintenance

Fish and Invertebrates to Consider For a 5 Gallon Fish Tank

Even though our options are pretty limited, there are still some really interesting choices. Let’s start with the most common ones (fish) and then move to invertebrates.

Fish for Small Tanks

While there are not many fish species that are suitable for tanks as small as 5 gallons (20 liters) because of preference to live in groups or high levels of activity which can be limited by little space. Nonetheless, popular fish species like Siamese fighting fish (Betta splendens) and the Least Killifish both qualify.

Least Killifish (Heterandia formosa) is definitely one of the smallest species of freshwater fish. Its characteristics include an olive coloration, transparent tail fin, and dark stripes which run laterally on both sides of their small body.

Due to their very little size (about 0.7 – 1.5 inches or 1.5 – 3 cm) and low temperament, a few Least Killifish can be housed in a 5-gallon fish tank.

Related article:

• Least Killifish – Detailed Guide: Care, Diet, and Breeding

Siamese fighting fish (Betta splendens) is a tropical fish species. They possess beautiful streamlined bodies and exceptionally long colorful fins that are delightful to see.

This small fish species will thrive in a clean tank with ample hiding places, do note that a single Betta fish is sufficient for a 5-gallon fish tank.

Ruby tetras (Axelrodia riesei) is another small species that does not require large tanks. These fish prefer soft, slightly acidic water and are best kept in a well-planted aquarium with plenty of hiding places. They are generally easy to care for and can be kept with other peaceful fish species.

Related article:

• Ruby Tetra – Detailed Guide: Care, Diet, and Breeding

Shrimp For Small Tanks

Other options for a 5-gallon tank are some species of freshwater ornamented shrimp. For example:

• Opae Ula Shrimp,
• Sulawesi Malawa shrimp,
• Cherry shrimp,
• Snowball shrimp,
• Caridina cf. Babaulti,
• Ghost shrimp, 
• Amano shrimp,
• Blue tiger shrimp, 
• Blue Velvet Shrimp.

Note: I would not recommend keeping most Caridina species in small tanks. The main problem is that shrimp need consistency. They require good water quality to thrive. Your water parameters should be as stable as possible. Unfortunately, it can be hard to achieve in small tanks if you do not have enough experience.

Snails For Small Tanks

Freshwater snails are an amazing choice for a 5-gallon tank. They are very hardy and can tolerate a wide range of water parameters. In addition, they will keep your tank clean from algae, detritus, and will benefit your aquarium in many other ways.

Some snail species for a 5-gallon tank:

• Nerite snails,
• Ramshorn snails,
• Malaysian Trumpet snails,
• Asolene spixi.

Note: Do your research (on my blog you will find detailed guides on most freshwater snails), many snail species are hermaphrodites. It can start with a few and turn into many very fast. If you do not want that, I would say that Nerite snail will be the best option.

Crayfish For Small Tanks

Although crayfish are a somewhat unorthodox pet, more and more aquarists are giving crayfish keeping a try. However, it can be intimidating as a first-time crayfish owner to learn how to care for these unique animals.

Be very careful, there are many crayfish species and most of them are absolutely not suitable for a 5-gallon tank! Luckily, some crayfish species do not grow huge, for example:

• Dwarf Mexican crayfish
• Dwarf Texan Crayfish.

Note: Regardless of their size, all crayfish species can be aggressive from time to time to their tankmates. Therefore, I would not recommend keeping anything else with them.

Crabs For Small Tanks

Basically, everything that I said about crayfish can be applied to crabs as well. We have to choose crab species that are small enough to be kept in a 5-gallon tank. For example:

• Thai Micro crab
• Pom Pom Crab.

These crabs are pretty peaceful and will co-exist peacefully with shrimp and snails.
Note: There are also other crab species that can be kept in a 5-gallon tank. For example, Vampire crabs and Tangerine-head Crab. However, instead of an aquarium, they will require Paludarium, because they need more land than water.
For more information, you can read my article “Difference between Aquarium, Terrarium, Riparium, and Paludarium?”. 

Stocking Formula For a 5 Gallon Tank:

• 1 x Betta fish
• 2 x Least Killifish
• 10-20 x Cherry shrimp
• 3 x Amano or Ghost shrimp
• 1 x Dwarf crayfish
• 5 x Thai Micro crab
• 1 Pom Pom crab
• 1 x Nerite snail

Important: The aforementioned species are suitable for a 5-gallon tank but you should note that all of them cannot be housed at the same time in an aquarium because of the risk of a high bioload which is detrimental as well as varying behaviors/temperament.

Examples of some of these combinations for stocking:

You can either keep one of them or try out some of these combinations for stocking:

• 1x Betta fish & 1x Nerite snails.
• 3x Least Killifish & 1x Nerite snails.
• 5x Cherry shrimp & 1x Nerite snails.
• 5x Cherry shrimp & 1x Amano shrimp
• 5x Cherry shrimp & 3x Thai Micro crab.
• 1x Amano shrimp & 3x Thai Micro crab.

Keep a close eye on the Least Killifish and the Betta fish especially if you plan to keep it with Cherry shrimp; depending on fish personality, it may eat your shrimp. Although there have been some success stories of Bettas living with shrimp, it is definitely not a guarantee and I cannot recommend keeping them together at all.

Regarding Least Killifish, there should not be problems with adult shrimp, unless they have just molted. However, these fish will gladly catch and eat baby shrimp. So, you will not see any shrimp colony growth.

So just be on the lookout and have a contingency plan to rehouse the shrimp if such a situation occurs. Also, feed them always to ensure that they do not starve, or else they may turn to the tank inhabitants to quench their hunger.

Fish Species Unsuitable For a 5-Gallon Tank

Regardless of the common misconceptions that the following species are suitable options for stocking a 5-gallon fish tank, I would like to use this opportunity to dispel such inaccurate information.

1. Neon tetras: Neon tetras are ideally suited to small tanks due to their small sizes and reduced activity levels. They are best kept in groups of 6 or more specimens preferably in a 10-gallon tank or larger tanks that can provide ample swimming space and vegetation.
2. Zebra & Celestial Pearl Danios: Despite their small sizes, often  2 inches (3 – 5 cm) or slightly above, they are highly active and best kept in schools of 6 or more in a 10-gallon tank. In addition, Zebra Danio tends to be a little aggressive when kept in smaller groups like 3-4, so they are not in any way suitable for nano aquariums.
3. Guppies and Platies: These livebearers are ideal for a little bit larger tanks due to their increased activity levels. In larger tanks that best suit them, they can be kept in groups of one male to two females. Smaller tanks are not convenient for their breeding activities so you are better off not having them in your nano tank.
   Note: It is possible to keep 2 – 3 Guppies in a 5-gallon tank. However, considering how quickly they reproduce, it will become too small very soon.
4. Pygmy Cory: Pygmy Corydoras is a very active and gregarious fish that likes to shoal in groups in the mid-levels of an aquarium while they pick off small food particles from the substrate. They prefer to be kept in groups of 5 or more specimens in a clean tank with stable water parameters and for these reasons, this species is not ideal for a 5-gallon fish tank.
5. Dwarf Pufferfish: Due to lack of space, the Dwarf Pufferfish cannot be kept in a 5-gallon fish tank. Dwarf Pufferfish is a very demanding fish and requires good water quality, and this is difficult to achieve in nano tanks. Another problem is their feeding preferences. They shouldn’t be underestimated due to their size, they primarily feed on snails, small invertebrates, and insects.
6. White Cloud Mountain Minnow: This small fish species is very beautiful and a wonderful sight to behold in an aquarium, however, it can’t be introduced to a 5-gallon fish tank because it needs to be kept in a group of at least 6 specimens.
7. Apple and Mystery snails, Rabbit Snail, Japanese Trapdoor Snail, Black Devil Snail, Brotia Pagodula Snail, While all snails may seem like a perfect fit for nano aquariums due to their relatively small sizes, there are exceptions, try to avoid these snails not because they are dangerous but they grow so large and let off so much waste that can easily ruin the tank water.

Planting and Decorating

It is important to cultivate live plants in your nano aquarium for oxygenation, aesthetics and to provide lots of hiding places for the critters.

There are many species of live plants to choose from, that can suit your 5-gallon tank, for example: Java fern, Java moss, Anubias nana, Cryptocoryne parva, Marimo moss balls. Live plants do not just improve the aesthetics of a fish tank, they also contribute positively to the water quality.

Decors are interesting additions to aquariums because they aid in replicating the native habitats of fish, shrimp, snails, etc.

Add small pieces of driftwood, rock, and caves on the substrate where the tank inhabitants can hide, few of these should be okay for a 5-gallon tank. You wouldn’t want to completely fill up the small swimming area with lots of decorations. The overall aim is to create a balanced and healthy ecosystem for the tank inhabitants to ensure that they thrive for a long period.

In addition, plants and hiding places will help different species to co-exist in a community tank and get away from unwanted attention when needed.

In Conclusion

Stocking a 5-gallon fish tank is one thing that many aquarists don’t get right due to hearsay or inaccurate information which they may come across online and this makes them overstock the tank. Bad move!

To make it easier for you, I included suitable fish species and invertebrates as well as the ones to avoid, in addition to plants that best suit your 5-gallon fish tank.

As it is with most nano tanks, maintaining good water quality is difficult. So make sure to test your water parameters and carry out water changes to reduce the amount of nitrates in the aquarium, or else the tank water may become lethal to the tank inhabitants.