Choose the Best Fishies For Your 1 Gallon Tank

As a beginner, it’s understandable if you want to start small with a 1-gallon tank to keep suitable fish. But, a gallon is never enough for any fish, even the tiniest ones, to have a consistently healthy life. While some expert aquarists may succeed in maintaining smaller tanks with vigorous supervision, you’re better off starting with at least a 5-gallon starter tank. 

Moreover, it’s not only about the fish fitting into the tank. They must swim and explore their environment to have a stress-free life devoid of illnesses and trauma. A 1-gallon tank is comparatively more vulnerable to environmental changes and outbreaks than a larger tank. 

In this article, we’ll discuss when you may consider a smaller tank and when you mustn’t, and list a few fish that can be kept in smaller aquariums. 

Considerations for Using 1-Gallon Fish Tanks

1-Gallon Fish Tanks

Despite being aware of the dangers, there exist circumstances where you may find yourself using a small 1-gallon tank temporarily. These circumstances call for considerations to maintain a comparatively healthy environment for your fish. Let’s discuss them in detail: 

Type of Fish and Size

Fish, like other aquatic creatures, have evolved to live in open water across the world without any physical barriers. Aquariums, in contrast, limit them to a confined space and force them to adapt to the environment. Smaller aquariums, especially 1-gallon ones, limit their mobility even more, increasing stress and reducing lifespan.

As we’re mainly considering crisis scenarios, small and juvenile fish can be housed in 1-gallon bowls and tanks. However, depending on the fish species, they may eventually outgrow the small tank and need to be reallocated to a larger one.  

If you’re going for a more permanent type of solution with the 1-gallon tank, carefully study the fish’s requirements, adult size, preferences, and breathing habits. It’s better if you can find fish who breathe air as the dissolved oxygen in smaller tanks often gets dangerously low. 

Water Parameters and Quality Maintenance

A plethora of water parameters and quality maintenance categories must be practiced to keep your fish comparatively healthy in a 1-gallon tank. These include:

  • Ammonia (NH3) 

Fish and invertebrates produce ammonia as waste. In a larger tank, beneficial bacteria convert ammonia to less harmful nitrite and then nitrate. However, a 1-gallon tank has very little space for these bacteria to establish themselves, leading to dangerous ammonia spikes. Even a single fish can overwhelm the system. These tanks also often lack proper filtration. 

  • Nitrite (NO2)

Even if some ammonia conversion occurs, nitrite can quickly accumulate in your small tank due to the limited space for bacteria to further convert it to nitrate. Nitrite is toxic to fish and disrupts their ability to carry oxygen.

  • Nitrate (NO3) 

While less dangerous than ammonia or nitrite, nitrate levels can still rise quickly in a small tank. Regular water changes become crucial to prevent nitrate buildup, which can contribute to algae growth and stressful fish.

  • pH

Small tanks are sensitive to pH fluctuations. Water evaporates quickly, concentrating minerals that can alter pH. Decorations or even the type of plastic used in the tank can also impact pH. Maintaining a stable pH level is difficult in such a small volume.

Frequent water changes, daily or every other day, and ensuring proper filtration are the essential parts of owning a small tank. 

Temperature Fluctuations

Temperature Fluctuations in Aquarium

Small tanks are susceptible to rapid temperature swings due to ambient room temperature and sunlight. Heaters, in most cases, also aren’t practical for smaller volumes of water as they can present overheating issues. Cooling the tank in warmer months may also be challenging due to minimal surface evaporation and physical limitations.

For example, take a cup of water versus a pot of water. Adding a little hot water to the cup will drastically change the temperature, while it’ll barely affect the pot water. Any external heat source or change in room temperature can cause significant swings in 1-gallon tanks. 

Water itself has a heat buffering capacity, meaning it can absorb some amount of heat before the temperature changes dramatically. However, a smaller volume of water has a lower buffering capacity. This makes the temperature in a one-gallon tank even more susceptible to swings.

These fluctuations can be dangerous to your fish. They may develop: 

  • Stress 

Rapid temperature changes are stressful for fish, weakening their immune system and making them more susceptible to disease.

  • Cold Shock

A sudden drop in temperature can cause fish to go into cold shock. This can lead to disorientation, organ failure, and even death.

  • Heat Stress

Rapid temperature increases can cause heat stress. Symptoms include rapid breathing, lethargy, and bulging eyes. If not addressed, it can be fatal.

Less Dissolved Oxygen

In a 1-gallon tank, the circumstances are horrifically ideal to create an environment with less dissolved oxygen (DO). Here is how small size contributes to it: 

  • Limited Surface Area

Air and water come into contact at the surface, allowing oxygen to transfer from the air into the water. The greater the surface area, the better the interaction. A 1-gallon tank has a very small surface area compared to its volume, limiting the amount of oxygen that can enter the water.

  • Biological Oxygen Demand

Any living organism in the tank, including fish, shrimp, and even plants at night, consumes dissolved oxygen. In a small tank, even a tiny fish or a few shrimp have a relatively high BOD compared to the total volume of water. This high BOD quickly depletes the available oxygen.

  • Inefficient Gas Exchange

The inability or adversity to facilitate proper water movement in small tanks limits the exchange of gases between the water and the air. A 1-gallon tank is difficult to equip with proper filtration or aeration systems. Devoid of good water flow, the oxygen-depleted water at the bottom of the tank struggles to mix with the oxygenated layer, reducing the overall DO level.

  • Temperature Instability

As mentioned, temperature instability is a concern in smaller tanks. As colder water can hold more dissolved oxygen than warm water, temperature increases can lead to even lower DO levels.

Breeding and Display Tank

Reasonably often you’ll come across aquarists showcasing their small breeder or display tanks. It’s in most cases a part of their setup connected to a main larger tank and shares the same filtration and temperature maintenance system as the main tank. It’s usually done to isolate juvenile fish without bringing rapid changes to their ecosystem.  

Best Small Pets for 1-Gallon Tank

Considering the maintenance required, here are some pets or fish that you can keep in a small 1-gallon setup with reasonable filtration and temperature control systems. 

1. Shrimps


Certain dwarf shrimp species, including Cherry Shrimp, Red Bee Shrimp, and Amano Shrimp, can be kept safely in a 1-gallon tank. While they still may require a larger tank with a substantial population, a few individuals can live easily in a well-maintained 1-gallon tank with strict monitoring and frequent culling (excess shrimp removal). Shrimps also have a relatively low bioload.  

Avoid housing shrimp with any fish that might see them as prey. Snails can be good tank mates as they help clean up leftover food and algae. Live plants also are essential for a shrimp tank. They provide hiding spots, help with water quality, and offer a natural food source.

2. Snails


While a 1-gallon tank is too small for most fish, it can be a suitable home for certain types of snails. Among them, Mystery Snails, Dwarf Ramshorn Snails, and Nerite Snails are notable. Similar to shrimps, snails also have minimal bioload, meaning they produce less waste compared to fish. This reduces the strain on the small water volume and makes it easier to maintain good water quality.   

Snails have lower oxygen requirements than fish. This is important because a smaller tank has less surface area for oxygen exchange. Furthermore, most snail species are beneficial scavengers, eating leftover food and algae in the tank. This helps keep the tank clean and reduces waste buildup.

3. Aquatic Plants

aquatic plants in aquarium

Small aquatic plants are rather necessary for small 1-gallon tanks if you’re housing live creatures. In addition to being attractive, aquatic plants release oxygen into the water and absorb excess nutrients from the water column. These aid in stabilizing the ecosystem and replenishing the dissolved oxygen. However, if you’re interested in adding critters later, consider researching the plan types that suit shrimps and snails. 

Some aquatic plants that are suitable for 1-gallon tanks are: 

  • Water Sprite

A fast-growing, easy-care plant that provides good hiding spots for tiny tank inhabitants like shrimp or snails.

  • Dwarf Hairgrass

A low-growing carpeting plant that adds a lush green foreground to your tank.

A versatile moss that can be attached to rocks or driftwood, providing hiding places and surfaces for beneficial bacteria to grow.

A fast-growing, stem plant that helps to control nitrates and provides oxygen.

  • Water Clover

A delicate four-leaf clover-shaped plant that adds a unique touch to a small tank.

Best Fish for 5-Gallon Tanks

In contrast to the 1-gallon setups, 5-gallon tanks are much more stable in the small aquarium segment. Here are some fishies that you can keep safely in 5-gallon water: 

4. Bettas


Bettas come in a stunning array of vibrant colors and flowing fin types. They’re known for their curious personalities and will often interact with their owners, flaring their fins or following movement outside the tank.

They also are excellent candidates for 5-gallon tanks because of their minimal requirement of vast swimming areas. They’re naturally territorial and prefer densely planted environments with hiding spots. A 5-gallon tank provides ample room for them to explore and establish their territory.

Moreover, Bettas are generally hardy fish with moderate care requirements. Regular water changes (around 25% weekly) and a good filter are essential, but they’re not as demanding as some other fish with higher bioload.

5. Chili Rasboras

Chili Rasboras

Reaching only about 1 inch long at maturity Chili Rasboras don’t outgrow 5-gallon tanks when kept in a small school of 6 to 10. They create a dazzling display as they dart around the tank in groups. Chili Rasboras are also community tank compatible, co-existing with peaceful neighbors like shrimps, and snails. Their small size translates to minimal waste output, reducing the strain on your tank’s filtration system.

While Chili Rasboras can adapt to a wider range of water parameters, slightly acidic and soft water replicates their natural habitat. De-chlorinated tap water in most areas falls within this range, but some may require adjustments. They primarily eat tiny organisms like microplanktons in the tank and brine shrimp. 

6. Celestial Pearl Danio

Celestial Pearl Danios are beautiful and peaceful schooling fish that can be a great choice for a well-maintained 5-gallon tank. They are relatively easy to care for and don’t grow more than 0.6 inches in length, making a school of 6 suitable for 5-gallon small tanks. A planted tank is ideal for Celestial Pearl Danios. Live plants provide hiding places, help to maintain water quality, and offer a more natural environment.

They have an iridescent blue body with a scattering of pearly white dots and orange markings on their fins. Males tend to be more colorful than females, with a more vibrant red or orange color on their fins. Celestial Pearl Danios are omnivores and will accept a variety of flake food, pellets, frozen or live brine shrimp, bloodworms, and daphnia. Offering a variety of foods will ensure they get the nutrients they need.

7. Mountain Minnows

While there are a few types of mountain minnows, the most popular and suitable option for a 5-gallon tank is the White Cloud Mountain Minnow. As they only grow to about 1.5 inches long, Minnows are perfect for a small tank of 5 gallons. Moreover, they’re peaceful with other peaceful community fish species like Celestial Pearl Danios, Chili Rasboras, or Neon Tetras, if kept in larger tanks. 

For a 5-gallon tank, a good rule of thumb is to stock with no more than 6-8 White Cloud Mountain Minnows. This will help to ensure there is enough space for them to thrive. While they are relatively hardy fish that can tolerate a wider range of water conditions than some other fish, it’s still important to maintain good water quality.

8. Ember Tetras

Ember Tetras are an excellent choice for a well-maintained 5-gallon tank. Their small size, peaceful temperament, and vibrant orange coloration make them a popular addition to nano aquariums. They only grow to about 0.8 inches long in adulthood, making them optimum for small aquariums. They also are schooling fish and should be kept in a group of 6 or more to provide them with a sense of security. 

Ember Tetras are adaptable to a wide range of water parameters, thriving in slightly acidic to neutral water (pH 5.5-7.5) with a temperature range of 72-82°F. While most tap water falls within this range, it’s always a good idea to test your water before adding fish. You may use gravel or sand as substrates. Consider a dark-colored base to enhance the Ember Tetras’ vibrant orange color. 


Q: What fish need the smallest tank?

Shrimps, Snails, Ember Tetras, Mountain Minnows, Pearl Danios, and Chili Rasboras need the smaller tank to school and thrive. But, it’s always better to provide your fish with more space to swim and explore. Additionally, with smaller aquariums being harder to maintain, it’s better to not limit your choices to the tiniest solution.

Q: Is 1 gallon enough for a betta?

No, A Betta shouldn’t be kept in a 1-gallon tank as they need to actively swim and explore the environment to emulate their natural behavior. The minimum tank requirement for Bettas is 5 gallons with aquatic plants and a reasonable filtration system.

Q: How many guppies are in a 1-gallon tank?

Guppies grow relatively larger to an adulthood size of more than 2 inches. Therefore, a 1-gallon tank isn’t suitable to house even a single guppy. We recommend a minimum of 1.5-2 gallons of water per Guppy to sustain their ecosystem and help them thrive.

Q: Is 1 gallon enough for shrimp?

Smaller aquariums are never enough for any aquatic creatures, but you can safely keep a few dwarf shrimps in a 1-gallon tank with regular water changes and monitoring water parameters.

The Bottom Line

We’ve compiled a list of safe fishies that can be kept in 1-gallon tanks with the risks associated with keeping them in such a small ecosystem. We also have listed a few fish that can be kept in a slightly larger tank to provide you with alternatives. Hopefully, you’ll now be able to shortlist your favorite fish and keep it happy and healthy.

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