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As an individual who may have been enticed by the idea of a nano tank (tanks around 3-5 gallons) or even if you lack the space for a larger tank, and would enjoy the company of a finned friend, there is much controversy in terms of tank size. Ideally bigger will always be better for any aquarium species, and most fish species have requirements of aquariums at least 10 gallons or more.

A 3-gallon tank (11.8 inches x 7.9 inches x 7.1 inches estimated) or 11 liters, is rarely recommended in the aquarium trade, though with the right species and ratios of fish, can still be achieved. Though before getting into that it is important to know why the size of a tank is so crucial.

Why Tank Size Matters

According to a study on fish health about tank size, except for Goldfish, tank size will not determine the growth rate of aquarium fish. Factors such as waste build-up causing ammonia spikes, overcrowding, and the quality of living space for the fish species will affect the overall health and lifespan of your fish.

The main concern with tank size is that more frequent cleaning will be required, and more regular water changes. The size of your tank will also depend entirely on the exact species of fish and other aquatic inhabitants you are planning on keeping.

What Will Affect Your Choice Of Tank Size?

A few factors that will essentially affect your choice of tank size are:

1. The Type of Fish and aquatic organisms you want to keep.
2. The exact size the fish will grow to when mature.
3. Whether the species are shoaling and the size of groups they need to be kept in.
4. The space and aquarium set-up needs of the species.
5. Water parameters and temperature requirements of the species.
6. Whether they are sensitive to regular water changes and cleaning that may cause slight fluctuations.

Some Of The Coolest Fish Species For A 3 3-gallon Tank

With that said, here are a few species you can consider for a 3-gallon tank, with the right set-up and kept in operation rather than communal set-ups.

1. Guppy

The Guppy or Poecilia reticulata as scientifically known, is sometimes also referred to as the million fish or the rainbow fish. It is one of the world’s most popular freshwater aquarium fish, with the widest variety of colors and patterns. Guppies are originally from South America, though they can be found all over the world today. Go. Today, guppies generally live around one to three years with optimal care, though there are cases where they have reached over five years. Guppy males are generally much more colorful than the females, they are smaller and have larger fins and tails. Males are between 1.5– 3.5cm (0.6 – 1.4 Inches), and females are 3–6 cm (1.2–2.4 Inches).

• Tank Set-Up – Though the universal rule is five gallons per single guppy, you can get away with a 3-gallon tank, for a group of two or three guppies. That is essentially me to be kept in groups with a ratio of 1 male per 2 females. They can tolerate most water conditions and parameters, as well as climates, though. Climates of between 78–82°F (25.5–27.8°C) and a water pH of between 6.5 and 8.5 is desirable. Similarly, they prefer brackish water, so you can add a little salt to the tank. A well planted tank with a fine gravel or sandy substrate is suitable with a few hiding spots and plenty of open space for them to swim.
• Feeding – Ideally, slow eaters. They are omnivores and do enjoy a very diet. A staple of quality flakes or granules should be fed along with fresh vegetables and proteins Meat based foods such as bran shrimp, bloodworms and insect larvae can be fed live or frozen.
• Temperament – The guppy is an aquarium favorite because of its very social, friendly, and peaceful nature. It’s a shoaling fish that will get along with most other species.
• Breeding – Copies are enthusiastic breeders that will breed in any tank setup, regardless. Unfortunately, they do not make the best parents and tend to eat their own young. Guppies or live-bearing fish, which means that they give birth to live young rather than laying eggs. Breeding should only be attempted successfully by keeping the young fry in a separate tank.
• Color Variations – Fancy guppies as they are known, come in a vast variety of color variations, patterns, and even fin and tail shapes. Then again, there is also the Endler’s Live Bearer and Scarlet Livebearer, which are closely related to the guppy. The most basic guppy colors are:
  • Silver
  • Black
  • Blue
  • Green
  • Purple
  • Red

2. White Cloud Mountain Minnows

The White Cloud Mountain Minnow is a Coldwater Freshwater fish native to China, forming part of the Carp family. It has an adult size of roughly around 4 cm (1.5 inches). Cloud Minnows need to be kept in small groups, and no more than five are recommended for a 3-gallon tank.

• Water Parameters – Although the nominal temperature range for the species in the wild is, it can survive water temperatures down to 5 °C (41 °F).^[7] This makes it an ideal fish for keeping in an unheated aquarium in cold climates.
• Tank Set-Up – Ideally, they are extremely forgiving in terms of water parameters and temperatures, though colder water temperatures of 18–22 °C (64–72 °F), are favored, and a pH between 6.0 and 8.0. Avid jumpers, thus a lid for their tank is necessary. You can add some live plants and décor to simulate their natural habitat. White Cloud Minnows are much healthier and more active in colder water temperatures in general.
• Feeding – They are opportunists and omnivores feeding mostly on grasses and insect larvae. A diet of quality flakes or pellets, freshly blanched vegetables, and proteins such as bloodworms, insect larvae, and brine shrimps can be fed.
• Temperament – Minnows are peaceful shoaling fish that will flourish with other peaceful fish that can endure colder water conditions.
• Breeding – Minnows are generally easy to breed and will spawn daily if they are in optimal condition. They do unfortunately need a separate breeding tank, as the parents must be removed, because they tend to eat the eggs and fry.
• Color Variations – The White Cloud Mountain Minnow is silver-green, with bright red caudal and dorsal fins. There are several domesticated variations including the Rosy Pink, Golden, and other color morphs.

Lastly, the White Cloud Mountain Minnow is the ideal species for novice aquarists because it can easily flourish and breed in a wide range of water parameters and temperatures. In the right climates, a heater may not be required.

If you are looking for something a bit rarer and more impressive that will be perfect for your 3-gallon tank, the following two species are ideal tank mates.

3. Asian Stone Catfish

A tiny catfish species that reaches a maximum size of 3.7 cm (1.5), with a compact body, the Asian Stone Catfish is perfect for a three-gallon tank. It is native to the Asian rivers as well as India, and Bangladesh.

• Tank Set-Up – The Catfish prefers slow-moving currents and spaces to hide, with a sandy substrate in a naturally planted tank. Plenty of caves and bogwood can be added and dim filtered light. Temperatures of around 25 and 30°C (77 – 86̊ F), are ideal, and a pH of between 5.6 and 7.6.
• Feeding – Mostly carnivorous, the Asian Stone Catfish prefers live and frozen meat-based foods including bloodworms and brine shrimp, along with quality flaked food or pellets. Algae wafers and fresh vegetables may be given as occasional treats.
• Temperament – Known to be shy, peaceful, and perfectly fine on its own or with its species, the Asian Catfish will be an ideal tank mate for other Indian fish species, especially the Dario Dario, which will be the next selection
• Breeding – Not the easiest species to breed, though not impossible. A group of more females and males can be placed in a breeding tank for spawning. After the eggs are laid and fertilized the adult fish must be removed.
• Color Variations – An interesting fact is the Asian Stone Catfish can change color from light to dark to blend in with its surroundings, even the eyes change color. Generally, it has a dark brown to tan beige color with rough stripes and patterns that resemble a rock, hence the name “Asian Stone Catfish”.

4. Scarlet Badis

As mentioned, the Scarlet Badis, or Dario Dario is an excellent friend for the Asian Stone Catfish. It is the smallest known percoid (part of a bony fish species sub-group) fish species and a micro predator naturally feeding on small aquatic crustaceans, worms, and insect larvae. Generally, Dario Dario do not exceed 2 cm (0.79 inches), and they are easily sexed, males having much more prominent and vibrant colors and fins, and females relatively smaller and duller in appearance. They are native to India and will inhabit clear water streams with sandy gravel and denser vegetation.

• Tank Set-Up – The Scarlet Badis is easy to keep with enough research on the species. A nano 3-gallon tank will suffice for a male and female Badis. In a tank with more males, decorative details and plants will break up territories that can cause fights among males. It is important to know that the Scarlet Badis is sensitive to water parameters and temperatures, thus according to studies, these parameters must be kept; Temperatures 22.2-25.6°C (72 -78 °F), pH 6.5 – 7.5, and water hardness 5-15 dGh.
• Feeding – The Scarlet Badis is a predatory carnivore requiring a staple of quality pellet or flake foods. Additionally, live or frozen Grindal or Micro chopped bloodworms are ideal, as daphnia, and other very small live or frozen foods.
• Temperament – They are extremely territorial around food and space, especially the males, and are predatory fish. Ideally, they can be housed with more robust and peaceful fish.
• Breeding – An established male and female can be separated into a breeding tank with no other fish, and plenty of broad-leaved plants are required. The female will lay her eggs on a leaf and the male fertilizes them. The parents must be removed. The eggs hatch in a few days and the new fry will feed off the yolk sac, after which you can start feeding them a high fat and protein diet.
• Color Variations – The Scarlet Badis can vary in color from bright red to orange and silvery blue, with blue hues in the stripes and fins.

5. Bumblebee Goby

An interesting and popular smaller genus of goby is the Bumblebee Goby, which is around 4 cm (1.5 inches) in size, and ideal for nano aquariums. They are originally from South Asia and inhabit both freshwater and brackish water bodies. The Bumblebee Goby has a longer lifespan of around 5-8 years and is more suitable for knowledgeable aquarists.

• Tank Set-Up – A single Bumblebee Goby or at most two females and one male can be kept in a 3-gallon tank. A tank decorated with a sandy substrate, bogwood, rocks, and caves is ideal as they enjoy hiding spaces. Stronger currents are not appreciated by the species. They prefer temperatures of between 23 -28 °C (73.4-82.4°F) and a pH between 7.0 and 8.2.
• Feeding – Bumblebee Gobies are mostly carnivores and will accept mostly meat-based live or frozen foods such as bloodworms, daphnia, small snails, and brine shrimp.
• Temperament – They are well known to be peaceful and shy, claiming a part of the tank as their territory, and guarding it.
• Breeding – The Bumblebee Goby is challenging to breed. The female will lay eggs in a cave or hiding space, and the male will guard them until they hatch and become free-swimming after a few days.
• Color Variations – Bumblebee Gobies have very clear black and yellow uninterrupted stripes, with an elongated body and round belly. They have a mustard yellow base color, and usually four vertical black bands. Color variations such as paler yellow and darker orange yellows have been observed.

6. Chilli / Mosquito Rasbora

The Mosquito or Chilli Rasbora comes from the Boraras genus and is a ray-finned aquarium species native to the swamps of Indonesia. They are around 1.3 – 1.8 cm (0.5 – 0.7 inches) in size when mature and can live up to 8 years with proper care. Their tiny size makes them ideal to be kept in smaller aquariums.

• Tank Set-Up – these Rasboras require a more naturally planted tank with some hiding spots and open spaces for swimming. They require water temperatures of between 25 -28 °C (77-82.4°F), and pH levels around 6.5-7.0. Ideally, they need to be kept in groups of at least one male and two females.
• Feeding – Similarly more carnivorous Chili rasboras enjoy small meat-based life, or frozen foods including worms and insects, or larvae. They can be fed a staple diet of quality flakes and pellets. Keep in mind they are tiny fish!!!
• Temperament – Being very small, and shy shoaling fish it is best to keep them in groups, or with other similar-sized peaceful fish.
• Breeding – Under any preferable aquarium conditions the Chili rasboras will lay eggs and spawn. Unfortunately, they tend to eat or attack their young fry, thus a separate breeding tank is necessary.
• Color Variations – These are very small and slender fish, with vivid red colors, and a black band running down along the lateral line of their body. Generally, there is a blotch at the base of the caudal fin. They are found in red hues such as Scarlets and very dark oranges.

What About Bettas?

Betta Fish or Siamese Fighters as many know them are often seen kept in tiny bowls or containers, especially in pet stores. Essentially you could keep a single male in a 3-gallon tank by itself, however, females need to be kept in groups of four or more, so this would not be suitable.

Tank Maintenance

Regular tank maintenance will form and integral part with a smaller tank and you can follow these steps to keep the water clean and clear;

A weekly water change can be done by siphoning 25% of the tank water from the bottom and replacing it with new conditioned, and properly heated water.

Removing dead plant materials, and food waste daily will help to keep the tank clean.

Décor and filters need to be cleaned when required.

Failing to keep proper water parameters and a clean tank in such a small environment may lead to illnesses such as Ich, Fin Rot, and Dropsy, which are quite common in aquarium fish. Similarly, fish that are stressed in an overcrowded space are more prone to disease.

To Conclude

In addition, it would be advisable to opt for a larger tank rather than a smaller one for most fish species. However, exceptions can be achieved with the right set-up and regular maintenance, keeping the correct ratios of fish and species of fish.

Frequently Asked Questions