The Top 8 Smallest Fish in the World

Written by AZ Animals Staff
Published: May 6, 2021


Today we’re going to talk about the eight smallest known fish in the world. Some of these fish are commonly found in aquariums, and some are only found in small springs in Greece, but the one thing they all have in common is they are very, very small! The rankings for which fish are the smallest based on how long the smallest of the species is, which is sometimes all of them and sometimes only the male or the female. The maximum length of most of the fish on this list is measured in millimeters. If you live in the United States, you might not know the metric system very well, but there are about 25 millimeters in one standard inch. To put that into perspective in terms of fish, a common aquarium fish that most people consider very small is the neon tetra, which is about 30 millimeters long.

The #8 Smallest fish in the world: Celestial Pearl Danio

Smallest fish in the world: Celestial Pearl Danio
The Celestial Pearl Danio boast plenty of color from the white pearl like spots on their sides to the red coloration on the fins.

A popular fish for nano aquariums because of its diminutive size, first on our list is the Celestial Pearl Danio, more formally known as Danio margaritatus. This fish measures in at just barely under an inch or around 25 millimeters in length. The little beauties are a deep blue color on their bodies, with goldish white spots all over. Females have bright orange on their fins that fades to clear, whereas males have red and black on their fins, and both sexes have black lines on their fins. Celestial Pearl Danios are sometimes referred to as galaxy rasboras.

The #7 Smallest fish in the world: Corfu dwarf goby

The Knipowitschia goerneri, more commonly known as the Corfu dwarf goby, measures around 22 millimeters in length, or just under one inch. These goby are white or tan with brown speckles over the top halves of their bodies. They have a strangely uneven appearance, without the symmetry often found in fish, almost as if they were squeezed out of a tube with a shaky hand. This fish has only ever been found in a single lagoon in Greece, but when that body of water was surveyed in 1991, no specimens of Corfu dwarf goby could be located. For many years, the species was believed extinct. Some 20 years later, however, nine new Corfu dwarf goby were discovered living in the same lagoon. The IUCN Red List designates these fish as Data Deficient.

The #6 Smallest fish in the world: Chili Rasbora

Smallest fish in the world: Chili Rasbora
The Chili rasbora is sometimes also called the Mosquito rasbora. These brightly colored, tiny fish only grow to measure around half an inch in length, making them one of the smallest tropical aquarium fish you can buy.

The Chili Rasbora, or Boraras brigittae, is just over three-quarters of an inch long, at 19 millimeters. Chili Rasboras are very popular aquarium fish because of their bright, intense coloring, and they are popular additions to nano aquariums in particular because of their small size. They are a lovely dazzling red, with shiny black stripes on their fins and also one running along either side. They are native to Borneo and are sometimes called Mosquito Rasboras.

The #5 Smallest fish in the world: Midget dwarf goby

Smallest fish in the world: Midget dwarf goby
The Midget dwarf goby can mainly be found on oceanic drop-offs at depths of from 20 to 30 metres (66 to 98 ft).

The Trimmatom nanus, known commonly as the Midget dwarf goby, is number five on our list, with a length of about 10 millimeters. The Midget dwarf goby is a beautiful bright reddish-orange, with bulbous eyes and feathery-looking fins. These fish are native to the Maldives in the Indian Ocean. Despite having been discovered in 1981, not much information is available on these dwarf goby, but they are certainly very small and very pretty!

The #4 Smallest fish in the world: Dwarf pygmy goby

Smallest fish in the world: Dwarf pygmy goby
A colorless and nearly transparent species, the dwarf pygmy goby has a moderately elongated and robust body.

The male Dwarf pygmy goby, Pandaka pygmaea, also known as Phillipine goby, comes in at nine millimeters long or approximately one-third of one inch. This thin fish has a blunt head and is highly translucent. Their only real coloring is dark spots on their body and the base of their fins. Sadly, the Dwarf pygmy goby, which is found in Southeast Asia, is listed as Critically Endangered.

The #3 Smallest fish in the world: Paedocypris progenetica

Smallest fish in the world: Paedocypris progenetica
Paedocypris progenetica is a tiny species of cyprinid fish endemic to the Indonesian islands of Sumatra and Bintan where it is found in peat swamps and blackwater streams.

This tiny relative of the carp has no common name, but the Paedocypris progenetica is a pretty remarkable fish! The smallest specimen was a 7.9-millimeter female. These fish are found only in a small swamp in Indonesia and they live in peat that is 100 times more acidic than acid rain! They were originally found in 1996 but were not correctly identified as a new species until 2006.

The #2 Smallest fish in the world: Stout infantfish

Some argue that the Stout infantfish, scientific name Schindleria brevipinguis, is actually the smallest fish because it is the lightest fish of record and both the male and female are of a similar small size. There is some conflicting information about just how small the males are, as some list 6.5 millimeters as the maximum male size, while other sources say closer to 7.5 millimeters. Females are between eight to nine millimeters. Since even the smallest measurement of 6.5 millimeters is larger than 6.2 millimeters, regardless of the female size, we are putting the Stout infantfish at number two. This skinny, pale yellow infantfish looks a bit like a tiny banana and is most commonly found in the Great Barrier Reef of Australia.

The #1 Smallest fish in the world: Photocorynus spiniceps

Smallest fish in the world: Photocorynus spiniceps
The model of a female Photocorynus spiniceps at the Natural History Museum in London, England.

Photocorynus spiniceps, a type of anglerfish, is our smallest fish. The males, which are parasitic and attach to the much larger females, only reach a length of 6.2 millimeters long, which is less than a quarter of an inch! In contrast, the females can get up to 50 millimeters in length, which is twice as long as the eighth smallest fish on this list. If you didn’t know, anglerfish live in the deep sea and use a bio luminous bulb to trick their prey into swimming straight into their mouths. The female Photocorynus spiniceps, like other anglerfish, have teeth very similar to a Fangtooth, so their prey is unlikely to escape! The translucent males of this species, which look like wisps of crumpled tissue paper, spend most of their lives stuck onto the female and taking their nutrients from whatever she eats, so she is always eating for more than one.

Those are the eight smallest known fish as of 2021, but new animals are being discovered all the time and it is easy for tiny fish to hide. Maybe in a few years, the Stout infantfish and that male anglerfish won’t even make the top three!

Next Up: The Top 9 Smallest Dogs in the World