Fish Types and their Classification

Scientists specializing in the study of fish, professionally known as ichthyologists, classify fish types of today into four categories. Each class boasts essential differences that separate it from the others.

It can be tempting to think that one fish is very much the same as another. Indeed, in some ways, nothing could be closer to the truth. All fish require water to survive, breathe using gills and have appendages called fins. However, that’s where the reality of it ends.

The class Chondrichthyes, for example, contains the sharks, stingrays, and other cartilaginous fish. Instead of bones, these fish sport cartilage. Additionally, these fish have no gill flap to protect their series of five gills. This order is predominantly marine. 

Some freshwater aquarium fish do belong to this order – the freshwater stingrays for example. However, the large size and extremely high maintenance requirements of these fish make them inappropriate for more hobbyists. Additionally, these fish types are very expensive, often fetching several hundred dollars for a single specimen.

On the other hand, the class Actinopterygii contains most of the fish that we know and love. These fish types have bones, an operculum or gill flap covering their gills, and occur in both fresh and saltwater.  

It Runs in the Family, or Does It?

Not all of you reading this article will be familiar with taxonomy. For those of you who aren’t familiar with the principle behind taxonomy, we’ll take this juncture to tell you more. 

In human families, you can usually establish that people are related to one another through various family traits. Perhaps most members of the family have fused earlobes, or piercing blue eyes are predominant. One way or another, it’s usually possible to tell when people belong to a family.

In the same way, scientists try to put all fish types into families based on their characteristics. Perhaps all the fish in that family have one slightly longer spine right in the center of their dorsal fin, or they all have small teeth. This allows us to predict how individual species will act or how they’re likely to breed based on other fish in the family.

However, still, as with human families, it isn’t always all that easy. Sometimes, one of the family’s children will have a shock of red hair or blue eyes when everyone else has black hair and brown eyes. 

Is it because of a recessive gene? Something that has been hiding away until now? Or maybe, just maybe, is it something else?

Did great grandma Suzie have a hustle on the side with neighbor Bob, and that’s why grandpa Robert didn’t have great grandaddy Pete’s cleft chin? Because Robert was Bob’s son! And now, two generations later, Bob’s cleft chin and brown eyes have suddenly appeared in baby Lucy?

It may sound like an overly dramatic soap opera, but this is precisely the problem that taxonomists and ichthyologists face every day. There’s always that one species that just won’t fit. It’s like all the others in the family, but it has an extra-long spine or round fins instead of pointy.

Then, out of the blue, a stranger appears. A new species, from Southeast Asia, has the same characteristics: with round fins and an extra-long spine. Suddenly, a new family is formed. The second cousin once removed. Still related fish types, but slightly different!

So How Does That Affect Us?

Now that we are, hopefully, all on the same page about how the family tree works, we can take a closer look at how this website is organized. 

Here, with us, you will find three main categories: Fish by Water Level, Fish by Family, and Fish by Temperament. The website is constructed using that layout to help you quickly find a fish that you need information about. 

However, as far as families are concerned, you will find not only profiles of specific species but also particular families or groups of fish. 

Each family profile or group profile will tell you about the family’s temperament, feeding habits, typical breeding behavior, place of origin, and other relevant information.

If you don’t know which family the fish you’re looking for belongs to, don’t be concerned, you can use the search function built into every category page. You may even find additional profiles and relevant articles that you didn’t think to look for. 

However, let’s get back to the taxonomy for a moment.

Popular Families of Fish

Let’s have a quick look at some of the most popular freshwater fish types to help point you in the right direction. In time, this website may extend to saltwater fish as well. But, for the time being, we will be focusing on freshwater fish.


The family Anabantidae has contributed many firm favorites to the aquarium trade. All of the bettas, paradise fish and gouramis belong to this family. For the most part, these fish are relatively slender, many times with bright coloration. Commonly used breeding methods include building bubble nests and mouthbrooding.


The family Cichlidae is, without a doubt, one of the most popular families of fish. This family contributes species from all around the world. For the most part, however, Africa and South America are the main contributors.

South America produces the Angelfish, Ramirezi Cichlid, South American Dwarf Cichlids, Jack Dempsey Cichlid, Peacock Bass, and many others. This continent is also home to the Discus – the trade of which could easily feed a small, third-world country.

Africa offers up species like the Malawi Peacocks, the other Malawi Cichlids, Kribensis, Jewel Cichlids, and various Tilapia kinds.

Where breeding is concerned, the cichlids are fish that guard their young. Apart from that, their brewing methods are diverse and varied. 

Fish like Angelfish prefer to breed on broad-leaved plants or large, flat rocks. Others, like the Firemouth Cichlid, are pit-spawners. Males build a large pit in the soil to which he lures females to breed with them.

Some species, like the Kribensis or the shell dwellers from lake Tanganyika, breed in ‘caves.’ To be honest, as long as there’s a hole in it where they can lay their eggs and guard them, these fish are happy to breed there. They have been recorded to reproduce in everything from flower pots to snail shells and even human skulls (in the wild, of course).

Last but not least, the mouthbrooders deserve mention. Mouthbrooders in this family range from the Lake Victoria Mouthbrooder to Tropheus and Cyphotilapia.

Warning: if you decide to develop an obsession with this fish family, you will undoubtedly start sprouting Latin regularly, resulting in odd looks from friends and relatives (they’re worth it though).

These are some of the most diverse fish out there, and also some of the most popular.


This is another family that has contributed many firm favorites to the aquarium trades. Among the many different fish from this family are white cloud mountain minnows, danios, goldfish, and koi. Many of the freshwater sharks, like hi-fin, bicolor, and red-tailed sharks are also members of this family.

The fish in this group range from small species, such as Rasboras, cherry barbs, and danios to large fish like koi, goldfish, and some barbs.

The generally preferred method of breeding in this family is broadcast spawning. The fish produce thousands of eggs and leave them to their own devices. The theory is that at least some of the young must survive if they release enough of them (must be successful, judging by the amount of these fish we have in the wild and in the aquarium trade!).


The Poeciliidae are crisply divided into two groups: the livebearers and the killifish. This family is one of the most commonly kept in aquariums, offering favorites like guppies, swordtails, mollies, and platies.

The livebearers, as the name implies, commonly breed by producing live young. However, the killifish are typically scatter spawners, plant spawners, or (in the case of annual killifish) they bury their eggs in mud. 

Annual killifish live in temporary water sources that dry up at the end of the rainy season. When the droughts come, their eggs go into a dormancy state, only to hatch with the next rainy season, and recreate the cycle. 

Due to their fascinating life cycle, the annual killifish have also spawned (excuse the pun) an entire group of societies and hobbyists who breed and collect different species. The fact that the eggs can be dried and shipped means that it’s relatively easy to acquire new species.


Every family has its black sheep, which just won’t fit, and fish are certainly no different. However, knowing which family your fish are in can help you learn a lot about what their behavior is likely to reflect.

We must warn you, though, some families are highly addictive, and it’s not uncommon for aquarists to start specializing in these groups. It’s gratifying, but you may quickly have a wall of fish tanks!

We hope you’ve found this useful, and feel free to browse all of our family profiles for more information about the groups that interest you.

Johanan Viljoen

Johanan Viljoen


Johanan is a lover of animals, and fish-charmer of note. In other words, he finds fish charming. He also has over 10 years of experience in the hobby.