How Many Kinds Of Fish Are There In The World – An Aquarist’s Guide

Have you ever stood in front of your local fish store’s display tanks and wondered exactly how many kinds of fish are there in the world? It is a question that naturally arises when you see the staggering variety of shapes, colors, and behaviors in the hobby.

Whether you are a beginner setting up your first 10-gallon tank or an intermediate keeper managing a complex planted scape, understanding this diversity is fascinating. I remember my first time seeing a Discus alongside a Neon Tetra and being blown away that they were even in the same animal category.

In this guide, we are going to dive deep into the numbers, the classifications, and the incredible science behind aquatic life. By the end, you’ll have a much deeper appreciation for the fin-tastic world thriving beneath the surface of our planet’s waters.

The Grand Total: Current Estimates of Fish Species

When we ask how many kinds of fish are there in the world, the answer is constantly changing as scientists discover new species in deep trenches and remote rivers. Currently, there are approximately 34,000 to 35,000 recognized species of fish.

To put that in perspective, that is more than the total number of mammals, birds, reptiles, and amphibians combined. Fish are the most diverse group of vertebrates on Earth, occupying almost every conceivable watery habitat.

For us aquarists, this means the “menu” of potential pets is nearly endless, though only a small fraction are suitable for home life. From the tiny Paedocypris progenetica to the massive Whale Shark, the range is truly mind-boggling.

Why the Number Keeps Growing

You might think we have explored every corner of the globe, but the ocean remains largely a mystery. Every year, taxonomists describe about 200 to 300 new species, many of which come from the Amazon Basin or the deep sea.

This is why keeping an aquarium is so exciting; we are essentially keeping a piece of an ongoing biological discovery. Sometimes, a fish appears in the trade before it even has a formal scientific name!

The Three Main Groups of Fish

To understand how many kinds of fish are there in the world, we have to look at how they are classified. Scientists generally divide all fish into three primary groups based on their skeletal structure and physiological traits.

Understanding these groups helps you realize why a shark acts differently than a goldfish. It also helps you understand the evolutionary history of the pets swimming in your living room right now.

1. Agnatha: The Jawless Fish

These are the most primitive fish, and you won’t usually find them in a home aquarium. This group includes lampreys and hagfish, which lack traditional jaws and paired fins.

They have cartilaginous skeletons and are often eel-like in appearance. While they aren’t common in the hobby, they represent a vital branch of the fish family tree that has survived for millions of years.

2. Chondrichthyes: The Cartilaginous Fish

This group includes the “cool kids” of the ocean: sharks, rays, and skates. Instead of hard bone, their skeletons are made of flexible cartilage (the same stuff in your nose and ears).

In the aquarium hobby, some intermediate keepers house small rays or “sharks” (like the Bamboo Shark), but these require specialized care and massive tanks. They are known for their electroreception abilities, allowing them to sense prey in total darkness.

3. Osteichthyes: The Bony Fish

This is where the magic happens for most of us! About 95% of all fish species fall into this category. They have skeletons made of true bone, and most possess a swim bladder to help with buoyancy.

Whether you love Bettas, Guppies, Angelfish, or African Cichlids, you are keeping bony fish. This group is further divided into ray-finned fish (most of our pets) and lobe-finned fish (like the ancient Coelacanth).

Understanding exactly how many kinds of fish are there in the world

If we look closer at the sheer volume of species, we see an interesting divide between freshwater and saltwater environments. You might assume the vast oceans hold the most species, but the reality is quite surprising.

Even though freshwater covers only about 1% of the Earth’s surface, it is home to nearly 40% of all fish species. This incredible “density” of diversity is why the freshwater aquarium hobby is so rich with options.

Isolation in lakes and river systems leads to speciation. For example, the African Rift Lakes (Malawi, Tanganyika, and Victoria) have produced hundreds of unique cichlid species that exist nowhere else on the planet.

The Role of the Amazon River

The Amazon Basin is perhaps the most important region when discussing how many kinds of fish are there in the world. It holds thousands of species, many of which—like Tetras and Corydoras—are staples in our home tanks.

The sheer variety of niches in the Amazon, from “blackwater” flooded forests to fast-moving “whitewater” rapids, has allowed fish to evolve into specialized forms. This is why it’s so important for us to replicate these specific water parameters in our aquariums.

The Most Popular Fish Families for Aquarists

While there are tens of thousands of species, the aquarium hobby tends to focus on a few key families. Each of these families offers unique challenges and rewards for the keeper.

If you’re a beginner, don’t feel overwhelmed by the 34,000+ species! Most hobbyists start with these well-known groups that are hardy and readily available.

The Cyprinidae Family (Barbs, Danios, Goldfish)

This is the largest family of freshwater fish. From the energetic Zebra Danio to the elegant Comet Goldfish, Cyprinids are found all over the world. They are generally hardy and active, making them perfect for those just starting out.

Most Cyprinids are egg-scatterers and enjoy being in schools. If you want a tank full of movement, this is the family for you!

The Characidae Family (Tetras)

If you love color, you likely have some Characins. This family includes the iconic Neon Tetra and the Cardinal Tetra. They are primarily found in Central and South America.

Most Tetras prefer soft, slightly acidic water. They are “schooling” fish, meaning they feel safest and look best when kept in groups of at least six to ten individuals.

The Cichlidae Family (Cichlids)

Cichlids are famous for their intelligence and complex parental care. From the tiny Apistogramma to the massive Oscar, this family offers incredible personality.

They are found in Africa, South America, and parts of Asia. Be warned: many cichlids are territorial, so you’ll need to research their specific social needs before adding them to a community tank.

How Many Kinds of Fish are Found in the Trade?

While there are over 34,000 species, only about 1,500 to 2,000 species are commonly found in the aquarium trade. This might seem like a small fraction, but it still offers enough variety to last a lifetime of keeping.

Of these, a significant portion are now captive-bred. This is great news for the environment! Captive-bred fish are usually hardier, more disease-resistant, and already accustomed to eating prepared flakes and pellets.

However, some rare species are still wild-caught. As responsible hobbyists, it is our job to ensure we are buying from sustainable sources to protect the wild populations that make up the global total of fish species.

The Rise of “Designer” Fish

In addition to natural species, the hobby has created many “strains” or “morphs.” Think of the endless varieties of Fancy Guppies or Long-fin Bettas. While these aren’t new species in the scientific sense, they add to the visual diversity available to us.

Always remember to prioritize the health and welfare of the fish over extreme physical traits. Some “balloon” varieties, for example, can have compromised swimming abilities.

Why Does Biodiversity Matter to You?

Understanding how many kinds of fish are there in the world isn’t just a trivia fact. It has practical applications for how you manage your tank. High biodiversity in nature means that every species has a specific “job” or niche.

In your aquarium, you can replicate this by creating a “balanced” community. You might have top-dwellers (like Hatchetfish), mid-water schoolers (like Rummy Nose Tetras), and bottom-dwellers (like Corydoras catfish).

By understanding the different kinds of fish and their natural roles, you can create an ecosystem where every inhabitant thrives. This leads to a cleaner tank and happier, less stressed fish.

The Importance of Habitat Replication

Each “kind” of fish has evolved over millions of years to fit a specific environment. A fish from the hard, alkaline waters of Lake Malawi will not do well in the soft, acidic tea-colored waters of the Rio Negro.

Always research the natural habitat of the species you want to keep. It’s not just about the “kinds” of fish; it’s about the “kinds” of water they call home.

Threats to Global Fish Diversity

Sadly, when we talk about how many kinds of fish are there in the world, we must also acknowledge that many are under threat. Habitat destruction, pollution, and climate change are putting many species at risk of extinction.

As aquarists, we are often the “ambassadors” for these creatures. Many hobbyists have actually helped save species! For example, the Tequila Splitfin was once extinct in the wild but was kept alive by hobbyists and scientists before being successfully reintroduced.

By supporting sustainable practices and educating others about the beauty of fish, we help ensure that future generations can also ask the question of how many species exist and find a world still full of life.

FAQ: Common Questions About Fish Diversity

How many new fish species are found every year?

On average, scientists describe about 200 to 300 new species each year. Many of these are found in the deep sea or in unexplored tributaries of the Amazon and Congo rivers.

What is the most common fish in the world?

While hard to count exactly, the Bristlemouth (a small deep-sea fish) is often cited as the most numerous vertebrate on the planet. In the aquarium world, the Guppy and Neon Tetra are among the most common.

Are there more saltwater or freshwater fish?

There are slightly more saltwater species (about 58%), but the diversity in freshwater is much higher relative to the volume of water available. Freshwater is a “hotbed” for evolution.

Which family of fish is the largest?

The Cyprinidae family (carp and minnows) is the largest family of freshwater fish, while the Gobiidae (gobies) is one of the largest families in the marine world.

Is a jellyfish or a starfish a “kind of fish”?

Actually, no! Despite their names, jellyfish and starfish are invertebrates. True fish are vertebrates with backbones. This is why many scientists prefer the terms “jellies” and “sea stars.”

Conclusion: Appreciating the Vast World of Fish

So, how many kinds of fish are there in the world? With over 34,000 species and counting, the answer is a testament to the incredible resilience and creativity of nature. From the smallest goby to the largest shark, every species plays a role in the global ecosystem.

As an aquarist, you have the unique privilege of bringing a tiny portion of this vast biodiversity into your home. Whether you keep a single Betta or a massive community tank, you are participating in a hobby that celebrates the wonders of life on Earth.

Don’t be afraid to keep learning and exploring! The more you understand about the different kinds of fish, the better keeper you will become. Happy fish keeping, and may your aquarium always be a thriving, diverse world of its own!