Keeping fish can be a fun and rewarding hobby, but it does require proper care and maintenance to keep your aquarium fish healthy. When it comes to small aquariums, like a 3 gallon tank, your options for fish are fairly limited. The general rule is 1 inch of fully grown fish per 1 gallon of water, so obviously large fish like Oscar Fish or Common Plecos that can grow 12 inches or more are out of the question for a small tank. But with the proper filtration, heating, and care there are still several suitable fish for a 3 gallon tank.
Quick Answer: Betta, Guppies, Tetras, White Clouds
Some of the most popular choices for small 3 gallon tanks are:
- Bettas – A single male Betta is one of the best options for a 3 gallon tank. Female Bettas can work too if there is only 1.
- Guppies – You could keep 3-5 male Guppies or a small group of females in a 3 gallon.
- Tetras – A small shoal of 4-5 small Tetras like Ember Tetras or Neon Tetras can work.
- White Cloud Mountain Minnows – This hardy minnow makes a nice small schooling fish for nano tanks.
The key things to keep in mind are stocking level, filtration, heater, and maintenance routine. You want to avoid overstocking a small 3 gallon tank but a few small peaceful community fish can thrive with proper care.
Stocking Levels For a 3 Gallon Tank
When it comes to stocking a 3 gallon aquarium, you need to be very conservative. These small tanks are suitable for housing 1-2 fish, plus possibly a few shrimp or snails. You want to avoid overstocking at all costs since water conditions can deteriorate rapidly in such a small amount of water.
Here are some general stocking guidelines for a 3 gallon fish tank:
- 1 Betta
- 1 Dwarf Gourami
- 3-4 small Tetras or Rasboras (like Neon Tetras, Ember Tetras, Chili Rasboras)
- 3-4 White Cloud Mountain Minnows
- 1 Dwarf Crayfish
- 5-7 small shrimp like Red Cherry Shrimp
- 1 Nerite Snail or 2-3 Ramshorn/Malaysian Trumpet Snails
It’s also possible to keep more than 1 male Guppy in a 3 gallon, but you need to monitor them for aggression and fighting. Female Guppies could work too but be prepared for breeding and a population explosion!
Most other common aquarium fish like Mollies, Platies, Swordtails, Danios, Corydoras Catfish, Plecos, Goldfish and more will inevitably outgrow a small 3 gallon tank, so should be avoided.
Avoid Overstocking
Never be tempted to overstock your 3 gallon aquarium. While you could physically fit more fish in the tank, it would put them under constant stress and deteriorate water quality and health. Follow the 1 inch of fish per 1 gallon rule to determine how many fish your tank can realistically support.
Best Fish for a 3 Gallon Tank
Let’s take a closer look at some particular species that are well-suited to nano tanks around 3 gallons in size.
Betta Fish
The Siamese Fighting Fish, or Betta, is one of the best fish for tiny tanks like 3 gallons. Male Bettas can live happily in a heated, filtered 3 gallon aquarium. Female Bettas can too, provided there is only 1 female per tank. Bettas are territorial and aggressive to their own kind. But a single Betta has minimal bioload and swims mostly at the top of the tank. They come in a variety of vivid colors and flowing fins. Make sure to give them plenty of plants or decor for hiding and resting near the surface.
White Cloud Mountain Minnow
White Clouds are hardy coldwater fish native to fast flowing streams in China. They stay small, around 1-1.5 inches, and are very peaceful shoaling fish. A small school of 4-6 White Clouds would work nicely in a planted 3 gallon aquarium. They prefer cooler water in the 60s Fahrenheit but can tolerate warmer tanks they just may be less active. No heater is needed for White Clouds.
Dwarf Crayfish
Dwarf Crayfish like the Cajun Dwarf Orange and Mexican Dwarf Crayfish are interesting critters that can live solitarily in a nano tank. They only grow around 2 inches in size and prefer planted tanks with hiding spots. A 3 gallon tank is sufficient for 1 dwarf cray but make sure to give them sinking food pellets daily along with algae wafers or blanched veggies to graze on.
Ember Tetra
The diminutive neon orange Ember Tetra grows under 1.5 inches and does well in softly acidic water. A school of 3-5 Ember Tetras could comfortably live in a mature 3 gallon planted aquarium. They’re very peaceful and make interesting nano fish. Provide them a varied diet of flake foods and micro pellets along with occasional frozen brine shrimp or daphnia for treats.
Endler’s Livebearer
Endler’s Livebearers are a small, vibrantly colored fish in the Poecilia genus. Males reach around 1-1.5 inches at maturity while females remain under an inch. A trio of 1 male and 2 female Endlers would work in a 3 gallon tank. They may breed frequently if happy so be prepared to move fry to another tank or sell them to your local fish store. Endler’s prefer slightly acidic soft water with plenty of plants to graze on algae.
Celestial Pearl Danio
The Celestial Pearl Danio is a beautiful nano fish from Myanmar that only grows to about .75 inches long. They have a shimmering cream and orange-red coloration and like to shoal in groups of 6 or more. A small school of 6 Celestials could be housed in a mature, cycled 3 gallon aquarium with fine gravel substrate and dense plantings. They’re peaceful community fish that add lots of color and activity to nano tanks.
Red Cherry Shrimp
Dwarf freshwater shrimp like Red Cherry Shrimp are perfect for small tanks because of their tiny size and low bioload. A 3 gallon aquarium could easily support 5-10 adult Red Cherry Shrimp. They require gentle water flow, stable water parameters, and plenty of hiding spots among plants and rockwork. They have a negligible bioload and help clean algae in the tank. Be sure to provide sinking shrimp pellets, blanched veggies, and calcium-rich foods too.
Best Plants for a 3 Gallon Tank
Adding live plants to your small 3 gallon aquarium can help stabilize water quality and parameters. Plants utilize dissolved wastes and help soak up nitrates. They also oxygenate the water and provide fish/shrimp with security and habitat. Here are some of the best beginner-friendly live plants for nano tanks like 3 gallons:
- Java Moss
- Java Fern
- Anubias Nana
- Cryptocorynes
- Amazon Sword
- Dwarf Sagittaria
- Marimo Moss Balls
- Duckweed
- Hornwort
- Rotala Indica
- Water Wisteria
- Pearl Weed
Aim for relatively easy, low light aquatic plants. Floating plants like Duckweed also help absorb excess nutrients. Use an LED nano aquarium light and aquarium plant fertilizers to nourish the plants without algae issues.
Filter Recommendations
Despite the small tank size, you still need effective filtration on a 3 gallon aquarium to maintain water quality. Small tanks are prone to dangerous ammonia and nitrite spikes since there is little dilution. An efficient filter paired with regular partial water changes is crucial.
For a 3 gallon tank, I recommend a hang-on-back style filter rated for 5-10 gallon tanks. Some popular choices include:
- Penn Plax Small World Filter
- Tetra Whisper Internal 3i Filter
- Marina Slim S10 Filter
- AquaClear 10 Power Filter
Aim for a filter turnover rate of at least 10x the water volume per hour. So the filter should have a pump output of around 30 gallons per hour or more. This ensures adequate circulation and filtration.
Another option is a sponge filter paired with an air pump. These provide gentle filtration suitable for nano fish like Tetras. Place the air pump on a timer to create periods of water movement then relaxation.
Cycling the Aquarium
Before adding any fish, it’s essential to properly cycle a new 3 gallon tank to establish beneficial bacteria. Cycling the tank involves growing populations of nitrifying bacteria that convert ammonia into nitrite then nitrate. This biological filtration keeps toxins in check. For a fishless cycle, add a source of ammonia and test until levels of ammonia and nitrites reach zero with some nitrates present. Then do a partial water change before adding fish stock a little at a time.
Heater Recommendations
Since water volume is so low in a nano 3 gallon aquarium, you’ll likely need a heater to maintain a stable, comfortable temperature for tropical fish. Small, nano heaters around 25-50 watts with an adjustable thermostat work best.
Some popular nano heater options include:
- Hygger Submersible Mini Fish Tank Heater
- Tetra Submersible Heater
- Aqueon Submersible Aquarium Heater
- Cobalt Aquatics Neo-Therm Heater
Set the heater to 72-78°F depending on the species kept. Use a separate thermometer to monitor tank temperature. Having stable temperatures in a small volume of water is crucial for fish health.
No Heater for Temperate Species
If you plan to keep temperate species like White Cloud Mountain Minnows that prefer cooler water in the 60s F, you likely don’t need a heater for a 3 gallon tank. Just monitor the temperature to make sure it’s in the appropriate range for the species.
Maintenance Schedule
While nano tanks look cute, they do require more frequent maintenance than large tanks to stay healthy. Expect to do partial water changes around 25% twice a week along with filter media rinsing or replacements. Test water parameters like ammonia, nitrite, nitrate 1-2 times per week and correct any issues. Top off evaporated water with dechlorinated water. Wipe down glass algae as needed and trim plants to keep the aquarium looking its best.
Create a consistent, weekly maintenance schedule like:
- Wednesday – 25% Water change, filter rinse, water tests
- Saturday – 25% water change, trim plants, wipe glass
- Sunday – Water top off
This helps maintain the nitrogen cycle and reduces the likelihood of illness or crashes in such a small tank.
Quarantine New Fish
When adding new fish, it’s wise to quarantine them for 2-4 weeks in a separate tank first. This prevents introduction of contagious diseases into your display tank. Quarantining gives you a chance to monitor fish health and treat any potential issues first.
Final Thoughts
A 3 gallon tank can make a beautiful nano aquarium but does require more care than larger tanks. Select your fish and plants carefully, invest in efficient filtration and heating, and perform frequent partial water changes. Adhere to the one inch of fish per gallon rule and you can have success!
Some peaceful fish like Bettas, Tetras, White Clouds, and shrimp truly thrive in planted 3 gallon nano aquariums. Take things slow by stocking gradually and maturing the tank first. Then you’ll be rewarded with a thriving slice of aquatic life even in a small tank.
