The unicornfish is a genus of fish that is otherwise known as Naso or Naso unicornis, and is part of the marine family Acanthuridae. They are a type of surgeonfish and have a very distinctive long nose. This long protrusion, or frontal horn, is compared to the horn of a unicorn. There are currently around 20 species within the genus, and they primarily live in coral reef environments.


Like their namesake, the unicornfish resembles the mythological unicorn, a horse-like animal with a giant horn on its head. Similarly, the unicornfish has a protruding nose or forehead. Some species of unicornfish have smaller noses, such as the well-named short-nosed unicornfish.

Remarkably, their iconic nose protrusion can grow to around 13 cm. They can grow to 61 cm, meaning that their noses are approximately one-quarter of their entire body length. Their bodies are predominantly oval-shaped and possess a defensive weapon in their scalpel-like fin. This is located on the side of the caudal peduncle.

The unusual frontal protrusion gives the unicornfish a very unique look
The unusual frontal protrusion gives the unicornfish a very unique look

The unicornfish is able to blend into its vibrant coral environment by taking on very bright hues of blue, green, yellow, and other colors. By taking on these colors, they become more effective at hiding from predators.


The majority of unicornfish species are found in tropical waters. Many of them inhabit the Indo-Pacific region and the seas around Hawaii. These fish are most commonly found in rocky reefs and coral reefs.

Many of these reefs actually rely on the unicornfish, as they play a fundamental role. Marine biologists will sometimes look at the unicornfish as an indicator of coral health.


They are mostly herbivore fish, and their diet base is algae, weeds, and other small plants. The specific algae they gravitate towards can range from red, green, and brown algae that grow on rocks and coral surfaces.

However, despite being herbivorous algae eaters, there are instances in which unicornfish feed on very small crustaceans. These fish tend to gather in small groups when it comes to feeding. They will operate mostly during the day.

In an aquarium environment, unicornfish can thrive off of various green foods, such as marine algae pellets, seaweed, and spirulina.


Overall, unicornfish are seen as pelagic breeders as they will release their gametes, or eggs, into the open water column. These eggs then flow with the current and hatch further down the line. Due to their tendency towards open-water breeding, it is rare that unicornfish breed in aquariums and captivity. Their inherent need for large areas of water makes it hard for breeding to occur.

The unicornfish are fairly long-living fish if all goes well. On average, they can live for around 15 years, which is quite impressive considering the brutal nature of life in the oceans.

The spotted unicornfish is one of many variations of the genus Naso
The spotted unicornfish is one of many variations of the genus Naso


Like many ocean fish, predators are always lurking around the corner. Some of the main predators of the unicornfish are blue jackfish and moray eels.

One of the largest threats to the unicornfish is the fishing trade. Due to their delicious meat, many fishermen seek them out, which can lead to overfishing. Another contributing factor is their unique look, which has led to the ornamental unicorn fish industry, as more and more people want them stuffed and put on display.

Some species, such as the Naso annulatus, possess toxic spines that can cause harm to animals
Some species, such as the Naso annulatus, possess toxic spines that can cause harm to animals

Diseases are prevalent in oceanic ecosystems, and the unicornfish is no less susceptible to them. White-spot syndrome is a widespread disease in the form of a parasite that feeds on its host. Like many species of fish and crustaceans, unicornfish are at risk.

The threat level to humans from the unicornfish is generally low. However, some specimens have been found carrying ciguatera, a toxic microorganism. If consumed, it can cause issues. Some species of unicornfish have venomous spines that can cause harm if touched.

Facts about the Unicornfish

  1. They rarely are able to breed in aquarium environments, as they require open water
  2. Unicornfish are largely herbivores, eating weeds, algae, and other sea plants
  3. They come in a wide variety of colors, from blue and yellow to green
  4. The main threats to unicornfish are overfishing, disease, and predators
  5. Some species are considered to be toxic due to their poisonous spines


Are unicornfish endangered?

Fortunately, the unicornfish holds the ‘least concern’ conservation status. This means that their population number is well within healthy ranges. However, habitat loss and overfishing remain a threat to the fish.

Why do unicornfish have horns?

It is speculated that the males use their horns in courtship as a sign of superiority to attract the females for mating.

Are unicornfish poisonous?

Although generally, the unicornfish is not poisonous, dangerous, or life-threatening if coming into contact with humans, it has been known to carry the microorganism ciguatera. Ciguatera can be toxic if ingested.

What do unicornfish eat?

Unicornfish mainly feed on algae, plants, and zooplankton within their coral reef environment.

What are unicornfish called?

There are a number of species within the unicornfish family with a variety of names. However, the Latin word for the unicornfish group is ‘Naso.’

About Ocean Info

At Ocean Info, we dive deep into ocean-related topics such as sealife, exploration of the sea, rivers, areas of geographical importance, sailing, and more.

We achieve this by having the best team create content - this ranges from marine experts, trained scuba divers, marine-related enthusiasts, and more.

Sea Anemone with Clownfish

Dive into more, the ocean is more than just a surface view

Bottlenose dolphins are known to help stranded humans back to the shore

8 of the Most Intelligent Marine Animals

From dolphins' awe-inspiring communication skills to orcas' social complexity, the ocean is home to some of the most intelligent marine animals.

Share to...