The Saltwater Fish Hub

Saltwater fish are extremely popular in the aquarium hobby. They are known for their vibrant colors and patterns and are often kept in colorful tanks alongside corals. The Saltwater Fish Hub is the place to start learning about these remarkable marine creatures.

What are saltwater fish?

Saltwater fish, also known as marine fish, are species of fish that live in salty water, like the water you find in the sea.

Sea water typically has a salinity of around 3.5%. Fish that live in this kind of water are saltwater fish, whereas fish that live in rivers, lakes and streams, which typically have salt levels of less than 1%, are known as freshwater fish.

What fish can live in saltwater?

To live in saltwater, a fish’s body needs to be specially adapted to avoid becoming dehydrated. While it might sound strange to talk about a fish becoming dehydrated when they live underwater, saltwater fish really do face this problem. The reason is a process called osmosis.

Osmosis causes the less salty water inside the fish’s body to be transferred to the saltier water on the outside (i.e. the seawater). If the fish didn’t replace this water, it would become dehydrated and die. Saltwater fish must therefore constantly drink in water to replace the water they lose due to osmosis.

Freshwater fish have the opposite problem. The water inside their bodies is saltier than the water on the outside. This means the process of osmosis works in the opposite direction, causing water from outside the fish to be absorbed into the fish’s body. The freshwater fish needs to urinate a lot to get rid of this excess water.

What fish can go in a saltwater tank?

Given enough space and the right conditions, any saltwater fish can theoretically go in a saltwater tank. However, some saltwater fish grow to a size that makes it impractical for them to live in a tank, some have special requirements that are very difficult to replicate in captivity, and some saltwater fish are protected species that aren’t for sale within the aquarium trade.

Fish that go well in a saltwater tank tend to be the smaller, more hardy and peaceful species. The fish being small means you don’t need as big a tank, being hardy means they can handle a wider range of conditions, so are easier to care for, and it is of course easier to keep less aggressive species alongside other fish.

Below, we list 18 of the most popular saltwater fish in the aquarium hobby. They’re not all small, hardy and peaceful – some are larger, need special conditions or are more aggressive – but they do represent common species and families of species that you often find in saltwater tanks.

Saltwater fish examples

A list of saltwater fish species that are often kept as pets. Explore 18 popular types of saltwater fish, with pictures.

ANGELFISH

There are saltwater fish known as angelfish, as well as freshwater angelfish
Not to be confused with freshwater angelfish, marine angelfish are saltwater fish that live on tropical reefs in the Pacific, Indian and Western Atlantic oceans.

iStock.com/Shur_ca

BLENNIES

Blennie are small saltwater fish that hide in holes
Possibly the cutest saltwater fish! Blennies grow to be around 3 inches long and like to hide and poke out from holes in rocky aquascapes.

iStock.com/MichaelStubblefield

BLOWFISH

A blowfish inflating itself to make itself much larger
Also known as porcupine fish because of their sharp spikes, blowfish are able to inflate their bodies to defend themselves from predators.

iStock.com/FtLaudGirl

BUTTERFLYFISH

Butterflyfish get their name because they look like butterflies
There are over 100 different species of butterflyfish. They have thin disc-shaped bodies and tend to be brightly coloured, like butterflies.

iStock.com/gracethang

CARDINALFISH

There are many types of cardinal fish kept in the home aquarium
Most types of cardinalfish live in saltwater, though there are freshwater varieties too. Most grow to around two inches and adapt well to life in an aquarium.

iStock.com/Alberto_Carrera

CHROMIS

Three blue-green chromis
Relatives of clownfish and damselfish, though generally less aggressive, chromis should be kept in schools of several individuals

iStock.com/Madelein_Wolf

CLOWNFISH

Two clownfish - probably the most popular type of saltwater fish
Clownfish are the only fish that can live in sea anemones without being stung. In return, the clownfish protect and clean the anemone.

iStock.com/Beto_Junior

DAMSELFISH

A yellow damselfish
Though they are only small fish – growing to around two inches long – damselfish are territorial and notorious for being aggressive.

iStock.com/Stéphane_ROCHON

DOTTYBACKS

A blue dottyback with a yellow tail. Unsurprisingly, this kind of saltwater fish has dots on its back.
Another small but aggressive fish. Dottybacks love to hide in small holes and caves and will defend this territory fiercely.

iStock.com/vojce

DRAGONETS

A colorful dragonet
Dragonets are slow-moving fish that like to stay close to the sandy surface of the aquarium. They have special dietary needs which can be a challenge.

iStock.com/vojce

GOBIES

A single goby resting on a sand surface
Gobies are small, carnivorous fish that live at the bottom of the aquarium. Many gobies like to burrow into sand or muddy surfaces.

iStock.com/RibeirodosSantos

HAWKFISH

A hawkfish. A hardy type of saltwater fish.
Hawkfish are hardy fish that adapt well to being kept in an aquarium. They like lots of hiding places and will eat shrimp and other small fish.

iStock.com/Alberto_Carrera

LIONFISH

A lion fish with its venomous spikes.
Due to their venomous spikes, lionfish have few predators in the wild. They’ve been labelled an invasive species as they kill other fish and reproduce quickly.

iStock.com/LauraDin

ROYAL GRAMMA BASSLETS

A purple and yellow Royal Gramma Basslet
Also known as the fairy basslet, the royal gramma basslet is a popular aquarium fish. Good for beginners, they are peaceful, hardy, and brightly colored.

iStock.com/vojce

SEA GOLDIES

A single sea Goldie
Male sea goldies live in a group with 5 to 10 females. Interestingly, if the male dies, one of the females will become a male to take their place!

iStock.com/Ashok_Bhattarai

TANGS

A royal blue tang
We’ve had Nemo (clownfish, above) and now we have Dory too! Blue tangs live on coral reefs and need a large tank to be kept in captivity.

iStock.com/barbaraaaa

TRIGGERFISH

A triggerfish with its distinctive large yellow lips
Though they are popular in the marine aquarium hobby, triggerfish are often aggressive and many species can grow to a large size.

iStock.com/slowmotiongli

WRASSES

One of the many varieties of saltwater fish in the wrasse family
There are actually over 600 species in the wrasse family, which means there’s a lot of variety. They are carnivores and like to live in shallow waters.

iStock.com/wrangel

What is the most popular saltwater fish?

Thanks to the movie Finding Nemo, the most popular saltwater fish is quite possibly the Clownfish.

Two clownfish defend their anemone home
Clownfish are probably the most popular saltwater fish.
iStock.com/Aneese

It’s easy to see why they are so popular. Clownfish are colorful, easy to care for, and they are usually quite active fish. Unlike some saltwater fish, they don’t hide away in caves or behind objects. Instead, they choose an area of the aquarium to claim as their territory and slowly swim around that spot.

Clownfish are also a fascinating type of fish to learn about. They have a symbiotic relationship with the sea anemone, which means that they live together and both species benefit from the relationship. The clownfish is the only type of fish that is able to live inside an anemone without being stung, which gives the fish a relatively safe place to live. While the anemone is kept clean by the clownfish and is also protected from predators, as the clownfish defend their anemone home.

What is the best saltwater fish for beginners?

Our pick for the best saltwater fish for beginners is the Royal Gramma Basslet. Also known as the Fairy Basslet.

A Royal Gramma Basslet, or Fairy Basslet, which is our choice for best saltwater fish for beginners
Perfect for beginners, the Royal Gramma Basslet is colorful, hardy, small and peaceful.
iStock.com/vojce

The reason that we think the Royal Gramma Basslet is the best saltwater fish for beginners is that it is small (so you won’t need a huge tank), peaceful (so it won’t fight with other fish), hardy (which makes it easier for beginners to care for), and colorful (so that it looks beautiful in the home aquarium.

If you want a beginner saltwater fish that has a beautiful appearance, a small size, is low maintenance and peaceful, we highly recommend the Royal Gramma Basslet.

What saltwater fish can go together?

There are lots of different saltwater fish that can go together in the same tank. The key is to choose small fish (so that you don’t need an enormous tank and so that each fish gets plenty of room) and to choose peaceful fish that aren’t going to fight or try to eat each other.

One possible combination could be to combine clownfish (which like to claim territory in one part of the aquarium) with hawkfish (which like to hide), gobies (which add interest at the bottom of the aquarium), and butterflyfish (which will swim around in the open, displaying their striking color patterns).

What saltwater fish is the easiest to breed?

If you’re interested in breeding saltwater fish then it’s important to know that some fish are easier to breed that others. To easily breed saltwater fish in captivity – particularly if you’re a beginner – we recommend choosing a species of saltwater fish that is among the easiest to breed.

Three of the easiest to breed saltwater fish are Blue Devil Damselfish, Neon Gobies and Peppermint Shrimp.

What should I read next?

If you’d like to learn more, we recommend exploring our saltwater fish articles or finding out more about freshwater fish, fish tanks, aquarium equipment, or aquarium plants.