Coral Reef Fish: Top 8 Best Lesser-Known Facts

9 mins read
colorful coral reef with many fishes and sea turtle
By: stockphoto-graf/Shutterstock

This post includes a complete guide on coral reef fish and why they are essential. Read on.

Coral reefs are underwater ecosystems that are also home to different fish species and other tiny sea animals. Coral reef fish are small fishes that live in association with the reef ecosystem. Coral reef ecosystems are pretty complex with many inhabitants, be it the same species or different, and hence, boast enormous biodiversity.

The coral reef ecosystem is of great value and importance, as over 8,000 species of fish, both small fish and some large fish, live in it. It is one of the most colorful ecosystems globally, and those who have done scuba diving or snorkeling in certain places like Australia or Polynesia will know for sure.

What Exactly Are Coral Reefs?

Coral reefs are a vulnerable underwater ecosystem that is the most diverse in the world. These reefs forms along the edges of continents or islands when the coral larvae of aquatic inhabitants attach to hard surfaces such as submerged rocks.

With time the coral grows and becomes home to thousands of coral polyps (the animals that help build the reefs). These coral colonies create the structure of the reefs.

Coral reefs are formed due to years and years of coexistence among fish, algae, and invertebrates. Most coral reefs are built by marine animals that create a rigid skeleton, known as stony corals, and grow best in warm, clear, shallow, and agitated water.

Coral Reefs
By: chonlasub woravichan/Shutterstock

Numerous species of fishes have coral to thank for the habitat structure and energy it provides. More than 600 kinds of fish of hard corals reside in the Indo-Pacific coral reef and 4000 to 5000 species of reef fishes. The mutual relationship between corals that helps build reefs and corals that rely on reefs for habitat and food. On the other side, corals also depend on other fishes’ grazing for their reproductive success.

Coral reefs are home to about 25-35% of marine life, including worms, fish, mollusks, sponges, crustaceans, tunicates, sea urchins, and other fish species. And that is why it is considered one of the best aquatic ecosystems and is also known as the rainforests of the sea.


The first coral reef appeared 485 million years ago at the onset of the Early Ordovician.

What Kind of Fish Are Mostly Found in Coral Reefs?

Over 15,000 coral reef fishes can be found or identified, and many of them are commercially important fish species. This includes a wide range of tiny, colorful fishes found amid corals as well as the whale shark, the large reef fishes. The earliest known fishes are thought to have existed around 500 million years ago; they are known as jawless fishes, which included Hagfish and lampreys. Some of the most common reef fish found in coral reefs include the snapper, red bass, clownfish, butterflyfish, several species of coral trout, small crustaceans, and many other species.

Even many marine tropical coral reefs fish can be found close to coral reefs. Some of the top predators of reefs are:

  • Sharks

    Source: Ferita Rahayuningsih/Shutterstock

Sharks are truly said to be the “king of the sea” because they often serve as the top predator in marine food chains, maintaining leading control over the whole ecosystem. Sharks have barely altered in terms of their physical makeup since they first began to evolve 420 million years ago. Accordingly, they have not been required to evolve because they’ve been perfectly suited to their surroundings and environment throughout the majority of their history.

  • Moray Eels

Moray eels are serpentine-shaped and inhabit holes, fissures, and tunnels in coral and rock. In addition to tiny fish, they also eat mollusks and crabs. Although they are almost top predators, they occasionally fall victim to sea snakes or barracuda.

  • Butterflyfishes

The butterflyfishes are the initial group of well-known coral reef fishes. The majority of butterfly fish are vibrantly colored and closely associated with corals. The bodies of all butterfly fish are spherical, thin, and tall, resembling plates.

Which is the Biggest Fish Found in Coral Reefs?

Well, the size, color, texture, and species of all coral reef fish are different. You will be amazed by the fish biology found in coral reefs. The entire ecosystem consists of many fish species, ranging from larger fish to small groups.

However, the biggest or largest of all coral reef fish is the Giant Grouper. This fish grows up to 8.9 feet long and weighs about 300 kgs.

Giant Grouper
By: Giant Grouper/Shutterstock

Now that you know what a coral reef is, what are the fishes found in coral reefs? How about checking up on some facts about coral reefs?

Exciting Facts About Coral Reef Habitat or Coral Reefs

By now, you know what a coral reef is, but there are many lesser-known facts about coral reefs that could interest you. So, check them out:

I. Coral Reefs Are of Different Types

Coral reefs can differ in their structures, formations, and locations. And depending on that, there are different types of coral reefs presently across the globe.

These are the following types of coral reefs:

Barrier Reef:

Must you have heard of the famous Great Barrier Reef from Australia, right? Well, that is one type. These reefs can be found close to the shore but have a massive population at specific locations, mainly where the sea drops sharply.

These reefs form lagoons, are rare, and take longer durations to grow fully.

Platform Reef:

These types of reefs are commonly found in shallow waters and are usually wider at the top. They can be located away from the coastline growing on the continental shelf. They grow into different shapes and sizes depending on the water and wind flow.

Shore Reef:

As the name suggests, these reefs grow near the shores. Shore reefs are not very wide but extend quite long along the coast for kilometers.


Another common type is a circular coral reef. Atolls take millions of years to form and consist of a lagoon in the middle. Found commonly in the Pacific and Indian oceans.

II. Coral Reefs Are Colorful Because of the Algae Population

Coral reefs are known for their vibrant and colorful appearance; the marine ecosystem, like the coral reef fish, is majorly attributed to this.

seaweed or sea algae at the rock surface in the beach.
By: mr. habs/Shutterstock

However, apart from them, the relationship of coral reefs with zooxanthellae also causes color changes. Zooxanthellae are algae that share a symbiotic relationship with coral reef fish and other polyps.

These zooxanthellae are of different colors and keep changing their colors across a broad spectrum, and they provide colors to the hard corals. They grow in other groups, even over dead coral.


A symbiotic relationship is one where one species benefits and the other remains unaffected.

III. Coral Reefs Grow at a Very Slow Rate

Coral reefs are known to grow very slowly. On average, it is calculated to produce about two centimeters per year. And if you consider the massive corals, they are the slowest growing species. They grow about 5-25 millimeters, on average, per year.

IV. Corals Grow Better Where Strong Currents Exist

Corals can be found majorly in tropical regions and in locations where strong currents exist. Corals grow better in calm waters, and currents are directly related to the water surface temperature.

Currents keep the water cool, and that temperature helps the growth of corals.

V. Corals Help Improve Seawater Quality

The polyps in corals are very sensitive to the external environment. Environmental factors such as salinity, pH, the temperature can cause changes in polyp growth.

things to do in long island
Image by Walkerssk from Pixabay copyright 2016

Due to this sensitivity, polyps have an in-built filtration system. This filtration system helps remove the particulate matter and ultimately improves the water quality.


These are just some common coral reef facts; now, let us learn more about coral reef fish because there’s a lot for you to know. Coral reef fish are pretty interesting to learn about.

Lesser Known Facts About Coral Reef Fish Population

One of the most colorful and diverse habitats of the coral reef is the coral reef fish. The coral reef fish are also some of the fishes that we love to eat, but more than that, these beautiful fishes with an extensive range of shapes and colors attract scuba divers and marine biology scientists.

The bold and bright colors of different coral reef fish are visually unmatched in the undersea kingdom, and these patterns are not just for being attractive but serve their purposes.

Let us now check out some of the facts that most people probably didn’t know about coral reef fish:

1. There Are Specific Functions Behind Each Color or Pattern

You know that coral reef fish are vibrant and colorful, but did you know that the body shape, dyes, or designs are for a purpose?

For instance, the red color of some coral reef fish appears black underwater; this then helps them to go unseen. Similarly, you will find stripes on many coral reef fish. These stripes help a coral reef fish camouflage itself against the coral.

The spotted patterns in particular coral reef fish species help them confuse predators of all sorts, even the larger ones.

2. ”Nemo” from Finding Nemo Is for Real

fish on nemo Dory and nemo
By: Evanox/Shutterstock

Everyone must be familiar with the orange and white clownfish, right? You might know him as “Nemo” from the movie Finding Nemo. There are real-life Nemos too. These fish species are one of the species in coral reef fish.

And not just Nemo; you can see his friend Dory too. It is a blue and yellow surgeonfish. And both of them fall under the category of prettiest coral reef fish.

3. Half a Billion People All Over the World Rely on Coral Reef Fish

Coral reefs provide shelter to many species of fish, which in turn provide food for humans. It works along the food chain. And it is estimated that about around 500 million people on average consume coral reef fish.

It provides food resources to millions of people.

4. Online Survey Says Pomacanthus Semicirculatus Is the Most Attractive Coral Reef Fish

By: Francois Libert/Flickr @All Rights Reserved

Well, the ugly vs. beautiful debate exists in the reef habitats too. The total fish abundance we find in coral reefs is somewhere compared to which is more attractive. Many fishes in corals are beautiful, but the one that stands out is the Pomacanthus semicirculatus, commonly known as the black and white fish, semicircle angelfish.

5. Labrichtys Unilineatus, The Least Attractive Coral Reef Fish

If there’s the most attractive fish, it is only evident that there will be the least attractive from the common species. One of the least beautiful coral reef fish is the Labrichtys unilinear, commonly known as the brown fish, tube lip wrasse.

6. The Moray Eel Help the Corals Breathe Better

Did you know that the fish in coral reefs have specific roles in the coral reef ecosystem? For instance, the moray eels, a family of eels (the fish that looks a tad bit like snakes), hunt crabs, other fish, and octopuses in the reef.

Due to their body shape, they can easily swim between the corals for hunting, which helps them breathe better. But, how?

Well, when they swim between the coral, they tear away algae on their way, and when the algae are cleared, the corals can breathe better.

7. Clown Triggerfish Is Known to Deter Potential Predators

Clown Triggerfish with a natural green backraund colorful
By: Halawi/Shutterstock

Balistoides conspicillum, aka the clown triggerfish, is one of the most pretty fish in the trigger family. This colorful fish isn’t really what it looks like. This species is known for its temper and over-aggressive nature. Triggers are aggressive feeders.

The clown species has largemouths that help with potential predators. Another member of the trigger family is the Orange-green triggerfish, which is known for its strong jaws that only a few prey species can escape.

8. Cardinal-Fish Boasts a Relative Rarity

Cardinalfish, which belong to a small species, are known to have a notable characteristic. Their dorsal fin is separated from a single protrusion into twin fins (how rare is that?). This is not something that is commonly found among reef-dwelling fishes.

Other Things to Know About Coral Reef Fishes

As beautiful coral reef fishes might look, there are some dangerous fishes out there too. One such is a sea anemone, which shares a mutualistic relationship with clownfish, but they have venomous stings that are harmful to other fish. Sea anemones have tiny toxic harpoons on their tentacles.

All of the polyps, including the fishes, have different survival mechanisms. For instance, the Gobies species can avoid predators by hiding in the sand or tucking themselves into coral crevices.

For their growth and survival, these fishes form different relationships with the corals or other polyps. All sorts of relationships can be seen, for example, mutualistic, symbiotic, or commensalism. Hawkfish have a commensalism relationship with fire coral (all credits to their pectoral fins).

The coral reef fish play a vital role in balancing the entire ecosystem, and essential residents. They act both as predators and prey, thereby negating the reef’s food web.

Moreover, many fish from coral reefs are also considered great candidates for the aquarium trade.

Ending Note

Do you now feel like you know much about coral reefs? Well, that is precisely our mission. This guide is to help you with your knowledge of coral reef fish.

Coral reefs are of vital importance to humans. But they are also a very fragile ecosystem, which needs immediate attention and protection. Coral reefs are disappearing gradually due to various environmental factors and fishing pressure.

So, now it is our moral duty to do our best to save them. We have already mentioned that the coral reef fish accounts for heavy consumption by humans. So, to keep balancing the food web, it is essential to protect these fish’s homes.

And it is also essential to appreciate the fish that are not visually beautiful, as only the beautiful coral reef fish are not crucial for the reef.

I hope this article has provided you with the much-needed information. If you have anything else on coral reef fish, feel free to share it with us.

Infographic That Presents 8 Most Beautiful Fish To Keep In Freshwater Aquarium
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Hola! This is Kritika. She is a part-time content writer, a full-time poet, and a Biotechnology graduate. She is the author of Dusk Till Dawn- her first poetry book which was published in 2018. To follow her writeups visit or check out her Instagram handle @ms.hazarika

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