What to Know About Rainbowfish

Reviewed by Vanesa Farmer, DVM on January 06, 2023

Aquarium enthusiasts are often on the lookout for colorful and exciting species that they can raise in their personal tanks. Rainbowfish are a broad category of fish that meet these requirements. 

But — like any pet — rainbowfish have unique care needs. Make sure that you know how to properly maintain these beautiful creatures before you decide to bring them home.

What Are Rainbowfish? 

The term rainbowfish is actually a generic name that’s used to describe many kinds of ray-finned fishes. It mostly refers to one specific family of freshwater fish

The scientific name for this family is Melanotaeniidae. It contains a number of subfamilies. Within these subfamilies, there are at least 17 different genera and a large, unknown number of species. 

The largest genus in this family is Melanotaenia. All of the specific species referenced here belong to this genus of rainbowfish. 

The term rainbowfish can also refer to some species in the Labridae family. But these are more commonly known as wrasses. These are all saltwater fish that are found in coral reefs around the world. Since only some of the species in this family are called rainbowfish, the majority of the information in this article focuses on the Melanotaeniidae family.

What Rainbowfish Are Available for Aquariums? 

Not all species of rainbowfish are available in the aquarium trade. In fact, some species have only been seen in the wild a handful of times. For example, the only evidence that we have for the existence of the corona rainbowfish — M. corona — comes from two male specimens that were found in an Indonesian river in 1911. 

Examples of species that you can find in many fish stores throughout the world include: 

  • M. goldiei — the goldie river rainbowfish
  • M. nigrans — the blackbanded rainbowfish
  • M. boesemani — Boeseman’s rainbowfish

Many of the rainbowfish that you’ll find at pet stores are bred in captivity. Boeseman’s rainbowfish for example has been raised in Indonesian aquatic farms since 1983. 

This is essential for the preservation of this species. In the 1980s Boeseman’s rainbowfish became such a popular aquarium pet that tens of thousands were harvested from their natural environment each year. Today this fish is considered critically endangered in its native habitat.

Where Can You Find Rainbowfish? 

Freshwater rainbowfish are native to the Eastern part of the globe. You can find them in the waterways of: 

  • Northern and Eastern Australia
  • New Guinea
  • Certain Indonesian Islands
  • Sulawesi
  • Madagascar 

As they evolved, many species of rainbowfish have adapted to very small, specific habitats. This is a biological phenomenon called endemism. It’s rare to find a single species spread throughout the entire family’s domain. Instead, you’ll only find them in a limited number of rivers, lakes, streams, and swamps. 

For example, the blackbanded rainbowfish is only found in Australia. M. rubrostriata — the red-striped rainbowfish — is only found in certain waterways in New Guinea and Indonesia. 

Most species prefer areas where there’s a lot of vegetation. This gives them places to shelter and hide.

What Are the Physical Characteristics of Rainbowfish? 

Most species of rainbowfish are small to medium-sized creatures. The majority of them are around 4.7 inches long — or less. The smallest is about two inches in length and the largest species (M. vanheurni) can reach close to eight inches in length.  

For the most part, these fish have large eyes and slightly flattened appearances. They come in a wide range of colors including: 

  • Yellow 
  • Teal
  • Red
  • Green
  • Orange 

Many of them also have bold black stripes and other distinct markings. Boeseman’s rainbowfish has a particularly striking color pattern. The front half of the fish is a blue-gray color and the tail end is a bright orange.  

The rainbowfish lifespan ultimately depends on the exact species that you’re raising and the quality of its environment.

What Do Rainbowfish Eat? 

In the wild, rainbowfish are omnivores. This means that they eat both plant and animal life. Individual species survive off of the creatures that are found in their environments. This includes a variety of: 

  • Insects
  • Insect larvae
  • Crustaceans
  • Algae — including green algae

You can feed them flake-style food in your aquarium since they’ve evolved to hunt for insects on the surfaces of their native waterways. Flakes float better than pellets, so they’re easier for rainbowfish to see. Ask an expert at your local pet store for the best brand recommendations.

Basics of Rainbowfish Care

You should only keep rainbowfish from the Melanotaeniidae family in freshwater aquarium set-ups. Before bringing your new pet home make sure that you haven’t accidentally acquired a wrasse with a rainbowfish name — like the redthroated rainbowfish. Since they’ve evolved in saltwater, putting a wrasse in your freshwater set-up would kill it. 

It’s best to keep rainbowfish in small groups because many species are social creatures and are used to living in schools. 

You can either keep multiple members of a single species in one tank or mix and match your species of rainbowfish. They also do well with other tropical community fish that share their native ranges and habitats. Examples include tetras and guppies. 

Since most species of rainbowfish are adapted to very specific environments, it can be difficult to find the right aquarium conditions for your pets. In general, it’s best to match your tank’s environment to a species' native habitat as closely as possible. For example: 

  • The best Goldie river rainbowfish temperature range is from 77 degrees Fahrenheit to 82.4 degrees Fahrenheit and they’re used to a pH range of seven to 7.8
  • Blackbanded rainbowfish prefer a temperature range of 64.4 degrees Fahrenheit to 75.2 degrees Fahrenheit and an acidic pH in the range of 5.2 to 5.6
  • Red-striped rainbowfish are adapted to a temperature range of 75.2 degrees Fahrenheit to 82.4 degrees Fahrenheit and a pH range of 5.6 to 7.4

Some species may be able to adapt to slightly different temperatures and pH ranges than they’re used to. General guidelines include a temperature of 70 to 79 degrees Fahrenheit, a pH of 6.5 to 8.5, and a water hardness of eight to 25 dGH. Talk to the store staff where you acquire your new pet for the most accurate advice on your particular species.

Rainbowfish Health Issues

Just like any kind of pet, fish can become sick. For example, they can develop problems like parasitic and bacterial infections. 

Unfortunately, there aren’t yet many veterinarians that work with aquarium pets. More and more veterinarians are going into the field of fish medicine. But most of them are trained to work with large-scale fish farms instead of individual pets. 

You can still try contacting your local veterinarian if you’re worried about your pet. Otherwise, try looking for an expert online or at a nearby pet store. 

Rainbowfish are beautiful additions to many different freshwater tank setups. Spend some time researching the different color patterns and tank requirements for each species before choosing the ones that are right for you.

Show Sources

Animal Diversity Web: “Labridae Wrasses,” “Melanotaenia boesemani Boeseman's rainbowfish.” 
Encyclopedia of Life: “Rainbowfish,” “Search Results: Rainbowfish.”
Fishbase: “Melanotaenia corona Allen, 1982,” “Melanotaenia goldiei (Macleay, 1883),” “Melanotaenia nigrans (Richardson, 1843),” “Melanotaenia rubrostriata (Ramsay & Ogilby, 1886).”  
Flinders University: “Successful sampling of rainbowfish ecotypes.”

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