The very nature of small fish suggests that it’s highly likely that we have yet to discover the smallest fish in the world.
The current record-holder is a deepwater anglerfish who hitches a ride on his much larger wife, which is probably the only way we noticed him.
All the fish on our list fall under an inch, ranging from only 0.24 inches to .98 inches (6.2 mm to 2.5 cm). To put the size of these tiny fish into perspective, the common neon tetra aquarium fish is1.5 inches (3.8 cm) long.
Our ranking is from smallest to largest, taking into account the smallest adult size of the fish’s species. Sometimes the ranking is gender-specific, and sometimes it’s not.
Some of the fish on our list are fish that hide out in ocean depths or that humans have only seen a handful of times. However, two are actually quite popular in the aquarium trade.
Since you should only have one inch of fish per aquarium gallon, hobbyists find that they can fit more of these tiny fish into their tanks. Read on to find a list of the eight smallest fish ranked and learn more about them.
Our list includes eight of the smallest fish that we’ve discovered in oceans and other bodies of water around the world:
- Photocorynus spiniceps: 0.24 to .29 inches (6.2 to 7.3 mm) male
- Stout infantfish: 0.24 to 0.26 inches (6.2 to 6.5 mm) female and 0.26 to 0.3 inches (6.5 to 7.5 mm) male
- Paedocypris progenetica: .39 inches (10 mm) for both the male and the female, with a 0.31 inches (7.9 mm) record for a female
- Dwarf pygmy goby: 0.35 to 0.43 inches (0.89 cm to 1.09 cm) male and 0.59 inches (1.5 cm) female
- Midget dwarf goby: 0.39 inches (1 cm) for both the male and female
- Chili Rasbora: 0.5 to 1.38 inches (1.27 to 3.5 cm) for both the male and female
- Corfu dwarf goby: 0.87 inches (22 mm) for both the male and female
- Celestial Pearl Danio: 0.79 to 0.98 inches (2 to 2.5 cm) for both the male and female
Let’s look a little more closely at the details of each of these species.
At 0.24 to .29 inches (6.2 to 7.3 mm), the smallest fish in the world is the male Photocorynus spiniceps. Not only is it the smallest fish in the world, but it’s also the world’s smallest known vertebrate.
The Photocorynus spiniceps is a type of anglerfish that lives in the deep ocean. Anglerfish have a bio-luminous bulb that tricks their prey into swimming into their mouths.
But, what prey could be smaller than this little guy? Well, he doesn’t have to worry too much about that since he’s a parasite.
The tiny, parasitic males attach themselves to the females, which are 721% larger at 1.97 inches (50 mm).
To put this size difference in perspective would be like having a short, 5-foot male human attaching himself to a skyscraper-sized female human over 41 feet tall.
Some females spend their entire 25- to 30-year life without encountering a male, while others end up with as many as eight tiny males catching a ride on their bodies.
Photocorynus spiniceps fish live in both tropical and subtropical water in the western Atlantic Ocean and on both sides of the Pacific Ocean.
Some people feel that the stout infantfish (Schindleria brevipinguis) should hold the title of smallest fish since both the male and female are tiny.
The female ranges from 0.24 to 0.26 inches (6.2 to 6.5 mm), while the male ranges from 0.26 to 0.3 inches (6.5 to 7.5 mm).
The fish gets its Latin name from brevis, which means short, and pinguis, which means stout. This name refers to how much shorter and thicker its body is than other Schindleria species.
However, it also has a short lifespan of only two months. The Stout Infantfish is native to the Western Pacific.
The fish is currently only known to live on the Great Barrier Reef, near Queensland, Australia, and on the Osprey Reef in the nearby Coral Sea.
The smallest Paedocypris progenetica we have on record is a 0.31 inches (7.9 mm) female. However, the standard length for both males and females is .39 inches (10 mm).
Their name comes from the Greek Paideios, meaning children, and Cypris, meaning Venus. Thus, their name means Children of Venus.
When scientists first found Paedocypris progenetica, they were declared the world’s smallest vertebrates. Now, the male Photocorynus spiniceps holds this title.
Paedocypris progenetica is a relative of the carp that lives only in 10-20 small swamps in Indonesia. The blackwater peat swamp they inhabit is highly acidic, with 100 times more acidity than acid rain.
Unfortunately, peat swamp forests are quickly disappearing in Southeast Asia. The International Union for Conservation of Nature (IUCN) accesses Paedocypris progenetica as a species whose numbers are in decline, placing them as a near-threatened species on their Red List.
The dwarf pygmy goby or Philippine goby (Pandaka pygmaea) males are 0.35 to 0.43 inches (0.89 cm to 1.09 cm), while the females grow to 0.59 inches (1.5 cm).
Dwarf pygymy gobies were first found in the Malabon River in Rizal, Philippines. Unfortunately, this area has experienced reclamation, and all the remaining water there is heavily polluted.
As of 2004, the dwarf pygmy goby was considered extinct in the Philippines. However, it’s possible to find them living in brackish waters and mangrove swamps in Indonesia. Data is deficient for IUCN to access its threat level.
Hobbyists imported the fish for the German aquarium trade in 1958, so it may be possible to find one for sale for the home aquarium, but they appear to be very rare.
Since there are over 2000 species of gobies, be aware that not every fish labeled as a pygmy goby or dwarf goby is the same species as a dwarf pygmy goby.
Both the male and female midget dwarf goby (Trimatom nanus) reach up to 0.39 inches (1 cm). In fact, until 2004, we thought the midget dwarf goby was the smallest vertebrate.
The midget dwarf goby is native to the western side of the Indian Ocean near the Chagos Archipelago and the Maldives. It also lives on the western side of the Pacific Ocean.
It’s most common at ocean drop-off depths of 66 to 80 feet (20 to 30 meters) and occasionally in outer reefs and lagoons at 16 to 115 feet (5 to 35 meters) deep.
The midget dwarf goby was discovered in 1981, but there’s still not a whole lot of information available about it since It tends to hide among rocks, corals, and macroalgae.
The life expectancy of the midget dwarf goby isn’t known, but scientists think that it’s several months.
The chili rasbora or mosquito rasbora (Boraras brigittae) can be as small as 0.5 inches (1.27 cm). However, its normal length is 0.7 to 1.38 inches (1.8 to 3.5 cm).
Chili rasbora fish live in inland wetlands of Western Indonesia and Sulawesi. Their population has decreased to 10,000 to 100,000 adult fish in the wild.
According to the IUCN, many of their blackwater habitats have been heavily degraded or entirely destroyed.
Many of the remaining peat swamp forests where they live are under threat from human activities, such as draining the area to convert their habitat into palm oil plantations.
Many aquarium hobbyists choose chili rasboras for their small size, beautiful red color, and peaceful schooling nature.
Unfortunately, overfishing for the aquarium trade has contributed to their declining population in the wild, which is why it’s essential to buy captive-bred rather than wild-caught chili rasboras.
The average size of the Corfu dwarf goby (Knipowitschia goerneri) is only 0.87 inches (22 mm). As its name suggests, the Corfu dwarf goby is a goby native to the Greek island of Corfu.
The species was first found in Corfu in one spring in 1983 and wasn’t seen again until 2014 when a Czech-Greek expedition found nine Corfu dwarf gobies in the Korission Lagoon of southern Corfu.
Unfortunately, with so few encounters with the fish, very little is known about it. Scientists and naturalists have not explored the area extensively since there are over 100 aquatic sites on the island.
Some of the threats in the area include dams, water management, water usage, and droughts.
Many of the fish in the area are considered to be extinct. However, some fish like the Corfu dwarf goby may have merely been overlooked. In the case of the Corfu dwarf goby, they’re easy to miss because of their cryptic behavior, brown and white coloring, and small size. Plus, there hasn’t been much of a search effort made to ascertain their status.
The Celestial pearl danio (Danio margaritatus) is also called the galaxy rasbora, despite being firmly in the Danio genus. It’s the largest fish on our list at 0.79 to 0.98 inches (2 to 2.5 cm). Still, it doesn’t break the 1-inch mark.
Celestial pearl danios are native to Myanmar, where they live in small, shallow ponds no more than 1 foot (30 cm) deep formed from seepages and springs.
The ponds are lush with a couple of types of Elodea and Anacharis or local grasses. Their habitats range as low as 71° to 75°F (22° to 24°C) in January.
Unfortunately, IUCN lists the celestial pearl danio as a species whose numbers are decreasing in the wild.
These gorgeous bronzy-green fish with pearly-white spots and red stripes on their fins took the aquarium trade by storm when they were first discovered in 2006.
Research indicates that conservation actions are necessary to protect their habitat, and more research is needed regarding the impact of the aquarium trade.
It’s possible and highly likely that we haven’t discovered the smallest fish yet. After all, finding a fish smaller than a quarter of an inch (6.4 mm) can be a challenge.
Currently, the smallest fish we know about is the Photocorynus spiniceps. We’ve also described seven other fish under one inch (2.5 cm). Most of the smallest fish ranked are fish that you’ll probably never see in person.
However, among these are two fish that are common in the aquarium trade: the chili rasbora and the celestial pearl danio.
If the idea of owning small fish appeals to you, you may consider adding them to your home aquarium. However, you should be aware that purchasing wild-caught chili rasboras and celestial pearl danios can contribute to their decline in the wild.