How many fish can I have in a 1-gallon tank?

Keeping fish in a 1-gallon tank can be challenging due to the small water volume. Generally, it is recommended to have at least 2-3 gallons for even the smallest fish species. However, with proper care and tank maintenance, a few small fish may be able to thrive in a 1-gallon tank.

Quick Answers

Here are some quick answers to common questions about stocking a 1-gallon fish tank:

  • No more than 1 betta fish
  • Or 1-2 guppies
  • Possibly a few shrimp or snails
  • Not suitable for most other fish – lack of swimming space
  • Requires frequent water changes – at least 25% twice a week
  • Heater and filter highly recommended for health
  • Plants help uptake waste – Floaters like hornwort good
  • Do not overfeed – causes waste buildup

Betta Fish

One of the only fish species that can be kept alone in a 1-gallon tank is a single betta fish. Bettas have low oxygen demands and originate from small stagnant pools in the wild. However, regular water changes will still be required for the health of the fish.

When selecting a betta, choose a healthy specimen with vibrant colors and flowing fins. Avoid fish that appear lethargic or have clamped fins. Make sure the betta has enough room to swim around and flare its gills.

Bettas are labyrinth fish, meaning they can breathe air directly from the surface. This allows them to thrive in low-oxygen environments. But they still require an adequately oxygenated tank. Having a filter and performing partial water changes will maintain oxygen levels.

Even though bettas can survive in 1 gallon tanks, they will be healthiest and happiest when given more room. Aim for at least 2.5 gallons if possible.

Betta Tank Setup

Here are some tips for setting up a 1-gallon betta tank:

  • Use a standard rectangular tank, not a tall vase
  • Add hiding spots like plants or caves
  • Use a small heater to keep water at 78-80°F
  • Get a mini hang-on-back filter or sponge filter
  • Add floating plants like hornwort or duckweed
  • Use a lid to prevent jumping
  • Monitor ammonia levels and nitrates
  • Change 25% of water twice a week

Betta Tank Mates

Bettas should be kept alone in a 1-gallon tank. There is not enough room for tank mates, and bettas are aggressive towards other fish in confined spaces.

In larger tanks, bettas may coexist with certain peaceful community fish. But a 1-gallon is too small for other fish.

Snails or shrimp can potentially be added once the tank is mature and stable. But adding too many could overload the bioload capacity of such a small tank. Start with just one or two trumpet snails, ramshorn snails, ghost shrimp or Amano shrimp.


Guppies are another option for a 1-gallon tank. They stay relatively small, have minimal oxygen needs, and do well in crowded conditions. A trio of male guppies or a pair of females could work.

Be selective when choosing guppies for a 1-gallon tank. Pick the smallest individuals you can find in the store. Avoid long-finned varieties like delta tails that may have trouble swimming.

Guppies are social and should be kept in groups. But more than 2-3 guppies will overload the tank’s biocapacity. Stick to 1-2 fish for a 1-gallon setup.

Guppy Tank Setup

Here are some tips for keeping guppies in a 1-gallon tank:

  • Use a rectangular tank for swimming room
  • Add lots of plants like hornwort, anacharis, or guppy grass
  • Get a mini sponge filter or hang-on-back
  • Maintain temperature around 74-78°F
  • Do 50% water changes twice a week
  • Test water parameters regularly
  • Feed high quality dried foods
  • Supplement diet with blanched veggies

Guppy Tank Mates

No other fish species should be kept with guppies in a 1-gallon tank. The tank is too small to properly house multiple fish together.

Snails and shrimp can potentially be added after the tank matures. But be conservative, starting with just 1 or 2 shrimp or a few small snails. Monitor water quality closely.

Other Fish Options

Most fish require at least 2-3 gallons of water, even small species. But here are a few other fish that may work in a 1-gallon tank:

  • Sparkling gourami
  • Celestial pearl danio
  • Endler’s livebearer
  • Least killifish
  • African dwarf frog

Stick to just 1 fish, focus on regular water changes, and keep a close eye on water parameters. Provide plenty of hiding spots and surface cover.

Tetras, barbs, goldfish, cory cats, pleco catfish, and other commonly sold species will fail to thrive in a 1-gallon tank. Avoid these fish for such a small setup.


Certain invertebrates like snails and shrimp can be housed in a 1-gallon tank. They have a low bioload and help eat excess food or algae.

Here are some invertebrates suited for 1-gallon tanks:

  • Red cherry shrimp
  • Ghost shrimp
  • Amano shrimp
  • Ramshorn snails
  • Trumpet snails
  • Nerite snails

Only keep 1-2 shrimp or a few small snails in a 1-gallon. They can produce a lot of waste for their size. Test ammonia and nitrates frequently.

Avoid crayfish, crabs, and other large invertebrates – they need more space. Also quarantine any new additions in a separate tank first to prevent spreading disease.

Planted Tank

Having live plants in a 1-gallon tank can help absorb fish waste and prevent ammonia spikes. Some good beginner plants include:

  • Java moss
  • Java fern
  • Anubias nana
  • Duckweed
  • Hornwort
  • Anacharis
  • Water wisteria

Focus on low-light plants that can grow in the tank’s conditions without added CO2. Floating plants are especially useful in small tanks to control light and absorb excess nutrients.

A basic LED aquarium light is sufficient for a 1-gallon planted tank. Avoid adding fertilizers and limit rooted plants to prevent disturbing the substrate.


Consistent tank maintenance is crucial for 1-gallon setups. The small water volume causes water parameters to fluctuate rapidly. Ammonia and nitrates can quickly reach toxic levels.

Here are some tips for proper maintenance:

  • Test water 1-2x per week for ammonia, nitrites, nitrates
  • Change at least 25% of water twice a week
  • Gravel vacuum substrate during water changes
  • Wipe down tank walls to remove algae
  • Check filter media monthly and rinse when needed
  • Remove uneaten food and waste daily
  • Ensure proper water movement and oxygenation

Do not rely on “self-cleaning” products or undersize filters. There is no replacement for regular partial water changes in small tanks.

Consider an automatic fish feeder to ensure consistent portions. Only feed as much as your fish will eat in 2-3 minutes.

Water Parameters

Ideal water parameters for a 1-gallon community tank are:

Temperature 74-78°F
pH 7.0-7.5
Ammonia 0 ppm
Nitrite 0 ppm
Nitrate Under 20 ppm

Use an aquarium heater and adjust temperature slowly. Monitor pH but avoid drastic adjustments. Focus on eliminating ammonia and nitrites completely through water changes.


Keeping fish in a 1-gallon tank can work but requires diligence. Select appropriate fish species, invest in filtration and plants, and stay on top of maintenance.

For beginners, it is better to start with larger 5-10 gallon tanks that are more forgiving. But seasoned aquarists may find success with specialized 1-gallon setups.

At the end of the day, focus on providing your fish with the best possible care. If water quality declines or fish seem stressed, consider upgrading to a larger tank.

With strict care and husbandry, a few small fish or inverts can thrive in 1-gallon tanks. But larger is always better when it comes to home aquariums.

Leave a Comment