What Are the Smallest Aquarium Fish

Aquarists usually look for small fish for their nano tank setups. Fortunately, there are numerous such species available. Moreover, many of them are easy to manage. However, proper research is required to find the optimal candidate for your tank.

This article is here to ease up your research task as you will learn about some of the smallest aquarium fish for various tanks, e.g., freshwater, saltwater, blackwater, coldwater, etc. Just scroll down the page or directly go to your desired section. Happy learning.

World’s Smallest Fish

The dwarf minnow or Paedocypris progenetica is the world’s smallest fish. The largest known minnow is only 10.3 mm long. Otherwise, mature females get 7.9 mm, and males get 9.3 mm long. They are native pet swamp forests of Sumatra, Indonesia. It mimics zebrafish larvae.

Aquarium Smallest Fish

As an aquarist, you can keep several small fish in your tank. Here are some of them.

The Smallest Coldwater Aquarium Fish

Having a coldwater aquarium comes with several benefits. For example, they require low maintenance, no heater, diverse vegetation, etc. In a cold water aquarium, the temperature does not exceed 72°F or 20°C. Here are some small coldwater species with their peculiarities.

White Cloud Mountain Minnow

White cloud mountain minnows are among the smallest coldwater aquarium species, i.e., 2.1 cm long. They are native to China, Hong Kong, and Vietnam. 18 – 26°C is the optimal water temperature for their growth.

• They have a silver body with a blue line running through their body.
• They can survive in less than 5°C water temperature.
• White cloud mountain minnows are among the critically endangered species.
• They are easy to breed in tanks.
• They eat aquatic plants besides aquatic insects.

Bristol Shubunkin Goldfish

The tail fin of the Bristol shubunkin goldfish gives them a unique look. These coldwater aquarium fish can grow up to 7.5 cm. They feel optimal between 60°F to 70°F.

• It’s a lab-grown fish, i.e., developed by the Bristol Aquarist Society.
• They have white cuddle fins that make them distinctive from the rest of the Shubunkin species.
• It is among rare fish species and is often known as a national treasure in the UK.
• It exhibits a calico color pattern with dominant blue and also has red, white, blue, black, and grey.
• Its Japanese name is “sierironisiki,” which means seven colors.

Smallest Coldwater Aquarium Fish

Hillstream loach

Hillstream loach is another freshwater and coldwater fish. They are native to fast-moving streams of rainforests in Asia and grow up to 5.0 to 7.6 cm. They thrive well at 20–27° C. High temperatures make them sick.

• They can cling to the rock in fast-moving streams due to their specialized fins.
• Females are larger and rounder than males.
• They graze on algae that grow on rock.
• They feel comfortable in groups.

Rosy Bitterling

Rosy bitterling is a beautiful small creature from the Amur River basin to the Pearl River basin in East Asia. Their average size lies between 4 to 8 cm. Their optimal temperature ranges between 64.4 to 75.2°F.

• They have a unique reproduction method. Females lay their eggs on the gills of freshwater mussels.
• Juveniles stay inside the mussels until they can swim.
• They are schooling fish and show a stressless life within a group of 6 or more.
• In adulthood, males are larger and more colorful than females.
• They are omnivores with a tendency toward carnivores.
• They live in ponds with abundant mussels.

The Smallest Freshwater and Saltwater Aquarium Fish

Here are some small freshwater and saltwater aquarium species and their peculiarities.

Mickey Mouse Platy

This easy-to-keep and colorful fish species is among small freshwater aquarium fish. Typically, they grow up to 1 or 3 cm. This small beauty is the native to east of Central America and southern Mexico.

• The black mark near the tail is the reason behind its name, i.e., it appears like a Mickey Mouse.
• Males are smaller and brighter, while females have numerous caudal fins.
• Adult males have gonopodium.
• They are live-bearing and omnivorous, peaceful,l and suitable to keep in a community fish tank.

Neon Tetras

Aquarists love to keep these small and beautiful fish in their tanks. They grow up to 4 cm and live for 5 to 10 years. These are native to the Amazon River basin in South America.

• They are shy, timed, and easily scared.
• Neon tetras prefer to live in dark and vegetated areas and try to blend in with the surroundings.
• They have two lines, blue and red. Blue starts from the nose and extends to two-thirds. Red starts from halfway and extends up to the tail.
• While breeding, they scatter their eggs among aquatic plants.

Cardinal Tetras

This freshwater beauty is known for its striking colors. They grow up to 3 cm and weigh up to 0.13 grams. These tetras are native to Colombia, Venezuela, and Brazil.

• They have a colorful body. A blue line starting from the nose reaches the tail and a red line at the bottom. The blue line is iridescent, i.e., changes color with the light.
• They are omnivores and become transparent at night.
• Females are larger and rounder than males.
• They are schooling. Sometimes, schools reach up to thousands.
• They lay about 500 eggs in the rainy season, and the eggs are light-sensitive.
• Cardinals prefer shadows and slow-moving waters.

Glowlight Tetra

They are small, peaceful, and among aquarist’s favorite species. These tropical freshwater beauties grow between 3 to 4 cm long. Essequibo River in Guyana, South America, is the house of these fish.

• They have silver or translucent bodies with orange or red stripes.
• They are schooling and live stress-free in at least a group of six.
• Slightly acidic water with 3 to 15 hardness.
• They are a great addition to a peaceful community tank.
• Floating plants and shadow areas make them feel at home.

Smallest Saltwater Aquarium Fish

Lyretail Damselfish

These strange-shaped brackish water fish belong to the Pomacentridae family. Damselfish are native to Indo-Pacific waters and 2-inch-long.

• They have deep purple to black bodies with yellow bases, and crescent-shaped tail fins.
• They are abundant in the Western Pacific Ocean.
• Damselfish have a toothless palate.
• They control the algal diversity.

Clown Goby

These small saltwater and reef tank fish are known for their bright yellow coloration. They grow up to 4 cm and are native to the Western Pacific Ocean, i.e., from the Japanese coast to the Great Barrier Reef.

• Unlike every other Gobie, they live around coral reefs and cling to the corals with fused pelvic fins.
• Their yellow color is a caution signal to potential predators. It is called an aposematism mechanism.
• They secret toxic mucus that tastes bitter to keep them from predators.
• They live in small groups and defend their community against other goby fish.

Trimma Goby

Trimma gobies are one of the smallest saltwater fish with a 1-inch length and suitable for nano tanks. They live in the western Pacific Ocean.

• These gobies have striking, colorful bodies with yellow, red, and orange coloration and irradiant spots on their body.
• They prefer to live around the reefs, crevices, and caves.
• Gobies are suitable for peaceful community tanks due to their docile and quiet nature.
• They often hang around the substrate and coral reefs.
• They are sensitive to water species.

Yellow Clownfish

Yellow clownfish or Orange Skunk Clownfish are distinctive saltwater species. These distinctive fish can grow up to 4 inches and live up to 5 to 10 years. They are native to the Indo-Pacific region.

• They have a vivid yellow color body with a white line that runs through the body.
• Clownfish have a symbiotic relationship with anemones.
• They are largely tolerant and can live in less-ideal conditions.
• They readily spawn at home aquariums.
• Generally, they are peaceful but become territorial near to anemones.

Smallest fish for aquarium

Smallest Fish for Blackwater Tanks

Blackwater does not mean dirty or polluted water. It is rich in organic matter that gives it coloration. This highly healthy water accompanies numerous species. Here is a list of small blackwater smallest fish for aquariums.

Chili Rasbora

Chili rasbora, or mosquito rasbora, are small and peaceful fish. These beginner-friendly Indonesian native fish can grow up to 1 inch long. They live in vegetated, slow-moving waters.

• Males are brighter than females. It becomes more intense during breeding.
• They have reddish-orange or red-colored bodies.
• They are peaceful and schooling.
• Chili rasbora has interesting and delightful swimming patterns in a group.
• They deposit their eggs on thin leaves and mosses.

Ember Tetra

Ember tetra belongs to the Characin family and was discovered in 1987. They grow up to 2 to 3 inches long. Slow-moving waters of the Araguaia River basin in Brazil are the native house of these fish.

• They have a semi-transparent body with red or orange coloration.
• Ember tetras are schooling and live in at least a group of 6 to 8 fish.
• They feed on an omnivorous diet.
• Slightly hot and hard-water conditions are optimal for their growth.
• Males are smaller, slim, and more colorful than their counterparts.

Pygmy Corydoras

This small fish belongs to the Callichthyidae family, another suitable small blackwater fish. These Madeira River basin species can grow up to 3.9 cm long.

• Their smaller size makes them suitable for nano tanks.
• They have black and white striped bodies.
• Pygmy corydoras are peaceful and community fish.
• They are bottom dwellers.
• The presence of large fish forces them to hide.

Sparkling Gourami

This small creature is known for its irradiance and clicking sound. It can typically grow up to 4 to 5 cm. Tropical ditches, small ponds, and paddy fields in Southeast Asia are the houses of these fish.

• They are the smallest fish in the labyrinth family.
• Sparkling gouramis have irradiant red, green, and blue color that creates a striking response in the right lighting.
• They have an arrowhead shape.
• In adulthood, males show more striking coloration with higher red spots.
• They croak with their pectoral mechanism.

Smallest Fish for Blackwater Tanks

Wrapping Up

The dwarf minnow is the smallest fish in the world. There is also a list of the smallest aquarium fish species for various tank setups. If you have a cold water tank, check the white cloud Minnow, Bristol Shubunkin Goldfish, etc.

Freshwater tanks also have numerous species like neon tetras, cardinal tetras, Micheky Mous Platy, etc. Similarly, saltwater and blackwater tanks also have various small and interesting fish species. I think it’s enough to introduce the smallest fish in an aquarium. Now, it’s time to go deep down in research for the selected species.

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