If you’ve snorkeled on a reef in the tropics, odds are you’ve seen damselfish. These small but colorful fish are staples in many aquatic habitats, but how much do you really know about damselfish? Dive in as we explore five fast facts about damselfish.

There are many different types of damselfish. 

There are about 250 species of damselfish in the family Pomacentridae, a group which also includes clownfish. They come in a range of colors and patterns, from the aptly named four striped damselfish to the vibrant blue damselfish. Across all species, there are a few things they have in common: Their bodies are deeper than they are wide, and they have forked tails. Plus, they don’t get too big—the largest damselfish, the Garibaldi, grows only to about a foot long. 

Damselfish are found in a wide range of habitats. 

Most damselfish are found in marine, or saltwater, habitats in the Atlantic and Indo-Pacific oceans. There are a few others found in brackish or freshwater habitats, like the (again, aptly named) freshwater damselfish. Damselfish are commonly found in warm, tropical regions, but they can also be seen in subtropical zones. Also, many species are popular as aquarium fish, so you might see one in a friend’s home aquarium. 

They pack a punch.

Damselfish are small, but they’re surprisingly mighty! Some damselfish species are extremely territorial, meaning they will fiercely defend their homes from threats, including other damselfish. They will quickly and aggressively swim towards intruders to scare them away from their territory. 

Sometimes they’re unwanted. 

A few species of damselfish are considered invasive, meaning they’re in areas where they don’t naturally live and are causing harm to the local environment. One invasive species is the regal damselfish which originated in the Indo-Pacific Ocean and is now found in the Gulf of Mexico and western Atlantic oceans. Scientists aren’t exactly sure how they got to their new ranges, but it could have happened with people dumping their aquariums or from regal damselfish hitching a ride on international oil rigs. 

They’re tiny gardeners. 

Some species of damselfish are “algae farmers,” meaning they actually nibble away at the habitat to cultivate algae growth. They bite unwanted algae to remove it, allowing other, more desirable algae species to grow. This is part of a balanced coral reef ecosystem, but there can also be too much of a good thing: Some damselfish can eat live coral tissue in their quest to create an algae garden. Too many damselfish can stress out an already stressed reef. 

Can’t get enough fun fish facts? Check out our Wildlife Fact Sheets and visit our Action Center to help protect all animals that live in the ocean.