Goldfish in an aquarium

A fish refers to a cold-blooded animal known to live in water owing to the presence of gills on its body. The rest of its frame is comprised of fins and an elongated body that is littered with scales. From the description above, we can decipher that they belong to the paraphyletic family of organisms. 

Scientists uncovered that the very first fish came around about 400 million years ago. Throughout the years, fish have proven to be an essential food resource, mainly since they are a source of various minerals, proteins, and vitamins. Here, you’ll read about some of the most exquisite types of fish out there.

Different types of fish.

Fresh and Salt Water Fish.

One of the ways in which fish can be identified is through their natural habitats. The most common types of fish are fresh and saltwater fish. You’ll find species like the neon tetra, Guppies, Goldfish, and Plecostomus in the former. The latter group contains fish like the Mackerel and Anchovies. Gradually, the study of fish has unearthed much more complex classes. These categories focus on several more traits.


These are another common species of freshwater fish. You’ll be surprised to learn that at full maturity, a goldfish can grow as long as 14 inches if it’s out in the wild. It is believed that the domestication of goldfish begun at least 2,000 years ago. Another interesting fact you might not be aware of is that goldfish did not always have its custom gold color. 

Goldfish in water

This has been a result of decades of breeding. Beforehand, they boasted a dullish green and grey hue. Goldfish have remarkable hearing and smelling senses. Their great hearing comes from the tiny bones located close to their skulls. These are said to provide a link between their inner ear and swim bladder. 


They are another popular choice for fish enthusiasts to keep in their Aquarium. It stems from the fact that Guppies are not only very easy to care for, but they also have a good temperament, which means that they can co-exist peacefully with other fish. To cap it all off, they are very colorful.

A guppy fish in an aquarium

Guppies can come in every bright color imaginable, so if you are looking for an aquarium with a riot of color, they are your best bet. At full maturity, the guppy can grow up to 2.4 inches. They also have a life span of about two years. Guppies are additionally omnivorous and generally consume a different range of plants and insects.

Neon Tetra.

This is one of the smallest and most popular types of freshwater fish out there today. The neon tetra only measures in at about 2.2 centimeters horizontally. They are also the most common type of fish for first-time fish owners to have, as they are relatively easy to care for. Because of this, they are also a popular choice in Aquariums.

Neon Tetra fish in focus
Neon Tetra fish

Neon Tetras’ pleasant disposition also means that they can live in harmony with other fish. This type of fish can come in a host of different bright colors, making it very visible in the dark. Because they are omnivorous, the Neon Tetra will consume a wide range of food, such as insects, worms, and plants.


These are a particular breed of catfish that have armored like plates all over their body. Another distinguishing feature that Plecs have is their suck shaped mouths, which they use to chow down a wide range of foods. These include algae, wafers, and even brine shrimp. Their food choice makes them omnivorous. The Plecostomus is also considered one of the trickiest fish species to breed in any given aquarium.

A Plecostomus fish in the water

Because of this, only a few renowned aquarists have managed to rear them in their aquariums. Managing them can also be difficult as they tend to jump out of the water from time to time. Plecs can live up to 20 years, and even longer in some cases. It is ill-advised to lump them alongside other fish species such as goldfish as plecs will try to suck on them. 


The first example of saltwater fish we will cover is the mackerel. These are torpedo shape-type fish with a line of small finlets located behind their anal fins. Another distinguishable feature they have is a slender forked tail. 

A school of mackerel fish.

Mackerels are omnivorous types of fish and can consume a wide range of food like fish eggs, planktons, small fish, and crustaceans. Mackerels reproduce around the early summer and springtime. They swim towards the coastline, where they lay their eggs. The common mackerel can grow up to 12 inches in length. They can be found along the coast of the North Atlantic Ocean.


They are another popular example of saltwater fish. Anchovies are scattered all across the Red Sea and the Mediterranean. Owing to their large numbers, they often run in large schools, a characteristic they share with the herring. Anchovies are relatively small insight, measuring in only at 8 inches max.

A school of anchovies.

This means that they can be used by fishermen as bait to catch much larger fish. Other than this, they are also a popular choice of fish as they are relatively abundant in omega-three fatty acids. Because of their intense flavor, however, they cannot be consumed in large amounts. As far as their diet is concerned, Anchovies can eat other smaller fish, newly hatched fish, and even plankton. 

Anadromous fish.

They are hatched in freshwaters. After this, these types of fish go on to spend a significant portion of their life in the sea before finding fresh waters again to hatch their eggs. In contrast, saltwater fish can only be found in the sea. This category comprises of fish like the beluga, the greater surgeons, and shad fish.


These are a species of fish that are abundant along the Black Sea and Caspian basins. The beluga is one of the largest species of bony fish in the world. They can compete with other species like the ocean sunfish and even the great white in relation to size. The largest recorded Beluga measured in at 7.2 meters.

A beluga fish in the wild

Both male and female Belugas are believed to attain full maturity at around 16 years old. The Beluga fish is trendy amongst fishermen, most of whom trap them for beluga caviar production. Overfishing has drastically affected the numbers of its wildlife population.


Sports fishermen widely prefer this fish species due to their ability to jump in the water frequently. While fishing, however, anglers must take caution to ensure that they return the American shad fish into the waters, for instance, after they have caught it. Their female counterparts, on the other hand, are often fished for their roe.

A shad fish on ice

The average height of this type of fish is 30 inches. They are also said to have a gestation period of about two weeks, after which they go on to live for three years before they reach maturity. The shad fish additionally depends on plankton for sustenance.

Diadromous fish.

Another common category of fish is the Diadromous fish, which inhabit both salt and fresh waters at random intervals. Here, we can find fish such as the brook trout, American eel, Sea Lamprey, and the Striped bass.

Brook trout.

The brook trout is a species of fish that belongs to the char family. This species is also wildly popular with competitive fly fishermen. Most brook trout inhabit spring ponds, small lakes, rivers, and even creeks because they typically prefer to inhabit clear and cold waters.

A brook trout fish.
Brook trout.

They are also omnivorous, consuming insects, crustaceans, other smaller fish, and mollusks. Their most recognizable physical traits include wormlike markings on their back, as well as white-reddish spots. On average, a brook trout can weigh up to six pounds at full maturity. This can take up to two years in total. 

American Eel.

These eels can be found on the eastern coast of North America. They are often mistaken for fish in the water because of their long, slender, snake-like body, and their color ranges from green to yellowish-brown to black. Interestingly, the females grow up to five feet, whereas the males only grow up to two feet.

A school of American eels

They are one of the few catadromous fish found in the Atlantic Ocean, which means that they live in freshwater rivers and spawn in the sea. American eels can live for up to twenty years and feed nocturnally on worms, eggs, insects, fish, and crabs.

Sea Lamprey.

They are an infamous kind of fish, often known as ‘vampire fish.’ This is due to the many rows of teeth found in their round and sucker-like mouth, as well as the fish’s parasitic lifestyle. Sea lampreys use their many sets of sharp teeth to first hook on to their victim and then use their rough tongue to work their way through to the host’s blood and body fluid.

A sea lamprey fish.
Sea lamprey.

One fish can kill up to forty pounds of fish per year! Since the fish has no natural predators, numbers have increased dramatically, which has caused problems for the ecosystems of the northern and western Atlantic Ocean.

Striped bass.

The striped bass is the largest of the basses found in temperate waters. These fish types average about two to three feet in length but can reach up to six feet and weigh one hundred and twenty-five pounds. The striped bass gets its name from the seven to eight dark continuous stripes found on either side of their body.

A striped bass fish
striped bass 

The striped bass is anadromous, which means that they spend most of their time in the sea and only migrate up rivers to spawn. The females are known as multiple spawners because, unlike salmon, they do not die after spawning and can spawn more than once a season.

Catadromous Fish.

They are known to live in freshwater. They only enter salt waters to spawn. In this category, we have examples like the European Flounder.

European Flounder.

Contrary to its name, the European flounder is not only found in European waters but also in waters close to the US and Canada, where the flounder was accidentally introduced. It is a flat, oval-shaped fish, which is mostly found on the bottom of sea beds. The flounder generally swims on one side, usually with its right eye pointing upwards. 

European flounder fish.
European flounder. 

This side of the fish can change color to suit its surroundings and, as a result, remain well hidden. However, because it easily takes the bait and is often found on inshore waters, the European Flounder is considered a popular sport fish.

Sand Fish.

They possess the ability to completely flatten themselves deep in the oceans’ sandy bottoms to avoid dangerous predators. This category encompasses fish like Cod, Flatfish, and the Grouper. 


This is a species of cold-water fish that ideally prefers to stay close to the ocean’s bottom, which implies that they only prefer deep water. A codfish is easily recognizable because of the dark spots scattered all across its body. Other than this, it also has a chin barbell and two anal fins.

A codfish in the wild

These types of fish can also take on a wide variety of colors, ranging from green, grey, and brown to black. When the cod is fully grown, it can reach up to 6 feet and weigh over 200 pounds. Cods feed on other relatively smaller fish. They also migrate quite frequently throughout their lifespan.


These are slender, oval-shaped fish that lie at the very base of the ocean floors. The flatfish can come in a host of different colors like brown, beige, and black. One exciting feature they have is the ability to camouflage themselves by taking on the ocean floor’s exact color.

A flatfish in an aquarium

At the inception of their life cycle, flatfish are shaped like normal fish, and they even swim along the surface. However, after a few weeks, they flatten, with their eyes even moving to one side. At this time, the flatfish are also said to change their natural color; their back significantly darkens.

The Grouper.

They are part of the fish family known as ‘Serranidae.’ All groupers are large-mouthed and heavy-bodied fish, which can reach up to one meter in length and forty-five kilograms in weight. Their jaws are very powerful, and they use them to crush prey such as small fish.

A grouper fish in the wild
The grouper. 

There are roughly 161 species of groupers, and they are generally found in warmer waters. The fact that groupers are protogynous hermaphrodites makes them particularly interesting. This means that these types of fish can change sex, usually starting life as a female and then transforming into males when there is a need for more males in their group. 

Blue Fish.

These are fish that typically pack a 6% and above fat content. Their higher fat percentage stems from the fact that they are designed to migrate and store fat for long-distance trips. They also have a higher blood count than the other species. Because they are not easy to digest, fish enthusiasts are often advised to cook them dry. Because they contain a good amount of omega level 3 fatty acids, they help people with heart problems. You’ll find fish like the Bluefin Tuna and the Herring in this group.

Bluefin Tuna.

This species of tuna is the largest of its kind, measuring up to 6.5 meters on average. Remarkably, it can also weigh up to 550 pounds. The Bluefin’s body is streamlined and entirely designed for endurance and speed. At times, the Bluefin can pull back its pectoral and dorsal fins, making it move relatively faster. 

A bluefin tuna fish.
bluefin tuna.

They are also omnivorous, feeding on smaller fish, squids, eels, and crustaceans to maintain their massive size. One of the most exciting details about the Bluefin tuna is that it is warm-blooded, which is a relatively rare trait in fish. Overfishing led to the plummeting number of the species. This led to conservative efforts being doubled to ensure that they do not go extinct.


The herring boast some of the largest numbers of fish in the world. As such, they usually journey in reasonably large groups. Some of their most popular traits include a streamlined body, tiny head, and metallic colored backs. Fully matured herrings can grow up to 15 inches. They typically consume fish larvae, copepods, planktons, and pteropods.

A school of herring fish
Herring fish. 

Because of the large schools they keep, herrings often serve as sustenance for other fish like tuna and salmon. Herrings are a great source of vitamin D, which helps strengthen the consumer’s teeth and bones. Because of this, they come highly recommended. Other than this, they are also rich in fatty acids.

White Fish.

These fish types have a relatively low fat count, making them much easier to eat once cooked. These include fish like sea bass, turbot, and scorpionfish.

Sea bass.

The Sea bass is a type of fish abundant in tropical and warm seas, particularly the shallow end. They have unique physical attributes such as a wide mouth, small scales, and an elongated body. It has a dorsal fin, which has a spiny section and a soft-ray part.

 A sea bass fish in the wild
A sea bass fish in the water.

The sea bass is a carnivorous species of fish that eat mollusks, other fish, and crustaceans. On average, these types of fish can reach up to two meters. It, therefore, comes as no surprise that they can also weigh as much as 500 pounds. They come in a variation of different colors as well.


They have a variety of different names, such as stonefish. This stems from the fact that they usually live at the very bottom of the ocean. Scorpionfish are typically scattered across the South Pacific and the Indian Ocean. They like these areas because of the abundance of coral reefs, which help them avoid other predators.

A scorpionfish in an aquarium

Scorpionfish also use these reefs to go after their prey. These types of fish are deadly predators equipped with venom that can render their potential prey immobile. Their venom is stored in their spines. Another exciting trait they have is their feathery fins. A fully grown scorpionfish usually measures about 2 meters vertically and can live up to 15 years.

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