The Australian rainbow fish is a common name for many closely related, very colorful species originally from Australia, Papua New Guinea, and Indonesia. All in all, there are nearly 50 varieties.

Fish keepers have been handling them since the late 1800s. They are very popular with intermediate to advanced keepers who care for mid-range to large aquariums.

Freshwater rainbow fish may not be the largest, but they are very active and make amazing, bright displays of color.

Do you know the best ways to care for your Australian rainbow fish? Read on because we have the information and tricks you need for their best care, maintenance, and breeding.


Listed tank sizes are the minimum
Size: Up to 2 inches (5cm)
Tank: 12 Gallons
Strata: Middle – top
pH: 6.0 to 7.5
Hardness: Soft to medium. dH range: 3-25
Temperature: 73 F to 82 F (22-28 C)
Order: Atheriniformes
Suborder: Atherinoidei
Family: Melanotaeniidae
Genera: Melanotaenia

Origin and Appearance

Rainbow fish are found in Australia, Papua New Guinea, and parts of Indonesia. As more is found out about their biogeography, more information becomes available about their actual distribution by subspecies.

Their native habitat is marshy terrain containing streams, rivers, lakes, and swamps with ample vegetation and little to no current. You can often find them under floating plants or associated with logs and other underwater structures.

Although rainbow fish are not listed as endangered, wild rainbow fish populations are threatened by drought, invasive species, and the loss of habitat from human development.

Harvesting of rainbow fish for the fish-keeping hobby still occurs. Much of it is conducted by dedicated hobbyists such as Gary Lange, who is a rainbow fish specialist and has identified many subspecies.

Most Australian freshwater fish, including the rainbow fish you find online and in stores, are produced commercially on farms in Southeast Asia and Florida. Some hobbyists have learned enough about their biology to successfully breed true specimens to make them more available in the US.

The Australian rainbow fish you will encounter has great species diversity under the family Melanotaeniidae. All are very similar in body shape, color, and temperament and, for the sake of fish keeping, are just called rainbow fish.

Sometimes called silver rainbow fish, members of these families have amazing species diversity while maintaining similar appearances. Elongated bodies with mostly flattened sides. They can have magnificent colors which give them their name. Generally, the fish will appear silver with hints of color.

Mature fish show their best colors in the morning and when breeding. Rainbow fish in full display will have shades or swaths of bright purple, blue, green, and yellow across their broad bodies.

Older Rainbow males can have humped backs and bodies. Most rainbow fish reach up to two to four inches in length and live up to five years.

Rainbows are busy fish. They are always on the move, exploring and interacting with their environment.


Rainbow fish are a schooling species and are happiest when kept in groups of eight or more.

One of the best things about Australian rainbow fish is the sturdiness. They are quite disease-resistant when in ideal conditions. The best way you can keep your fish healthy is by maintaining a healthy tank.

They are not a difficult species to care for. The complexity comes from managing the larger tanks and systems necessary for their health and wellbeing.

Aquariums should be sized to the particular variety of rainbow fish you are keeping. A good average is 50 gallons to keep a school of 6 to 10 fish. This will quickly scale up to 100 gallons or more if you are adding tank mates.

A good lid is important on Australian rainbow fish tanks. They are known for their leaping ability and could end up on your floor if you are not careful!

Ideal water temperatures for rainbow fish are between 74 to 78 F. If the room where you’ll keep your fish has an ambient temperature below 74 F, you should have an aquarium heater to keep it well in their range.

Below their ideal temp range, rainbow fish will lose their color and become sluggish. Continued exposure to colder temperatures will weaken them to the point of illness.

Water quality is equally important. Most rainbow fish do best in water with a pH of 6.5 to 7.5 and relatively soft water. Commercially bred fish have developed a greater tolerance for both pH and dH but what all rainbow fish have in common is the need for very clean water.

For this, a high-quality filtration system plus a clean and fill system are investments in the long-term health of your fish.

Most experienced rainbow fish keepers change out 10 percent to 15 percent of the tank water weekly, or 25 percent every other week, depending on the size of your tank and your tank mates. You will also need a supply of replacement water that is chemical-free, balanced, and at the right temperature for your habitat.

Aquascaping for Australian rainbow fish can be summed up as “less is more” when trying to mimic their natural habitat. Three inches of aquarium sand or fine gravel makes an ideal substrate. You want it deep enough to anchor your plants.

A mix of floating and anchored plants are a good mix for rainbow fish. Guppy grass and java moss give you the ability to have greenery at all levels of the tank. Plant the perimeter with the rooted plants so your rainbow fish have plenty of room to swim and explore.

Add a few rocks, pieces of natural or artificial logs, and you are done. A sparse display helps make your fish more visible, and especially in the mornings, it will be easier to see their wonderful colors.

Though Australian rainbow fish are hardy, they are not impervious to disease.

Two of the most commonly encountered diseases in rainbowfish aquariums are White Spot Disease (also known as Ich since it is caused by the parasite Ichthyophthirius multifilis) and Velvet (which is caused by a parasite called name).

Just as the name suggests, White Spot Disease causes white spots to form on the body of the fish, while Velvet gives the fish skin a velvety look.

If you maintain your tank, the most likely way for disease to enter the aquarium is through the introduction of new fish. A highly recommended practice is to quarantine any new additions for up to two weeks before introducing them to the tank. Try to purchase fish in person and visually select healthy specimens from a reseller who will guarantee their quality. If you do purchase aquarium fish online, be sure the reseller will guarantee their fish for at least 30 days.

Tank Mates

Rainbow fish are very peaceful against most fauna and make perfect tank mates for anything that will not try to eat them or engage in bullying or fin nipping.

Fishes that can thrive in the target temperature and water quality ranges will make good tank mates.

The Australian rainbow fish’s worst enemy is often itself. Two males may end up fighting each other during breeding times if there are not enough females for each of them.

Since you are keeping rainbow fish in schools of at least six fish, try to keep the balance of sexes weighted towards female fish. For example, in a group of six, have two males and four females. This will minimize the opportunity for aggression and keep everyone peaceful.

When selecting tank mates, remember that most compatible fish will be in schools, and each school needs room to swim. A multi-species tank should be 200 gallons or more.

– Here are some of our favorite tank mate choices:

Dwarf Gourami: These are small but colorful members of the species. They are peaceful schoolers that tend toward orange and red hues. Keep them in schools of 10 or more.

Pearl Gourami: They share the same temperament and like the same types of habitats. Pearl Gourami is an ideal choice especially when you are kitting out an aquarium of over 30 gallons. They do best in groups of six. .

Silver Dollars: Native to South America, the silver dollars fish can do well with the Australian rainbow fish. They are mostly peaceful, preferring the company of their species. They tend to leave other fish alone if they cannot fit them in their mouths.

Rosy Tetra: The Rosy Tetra, as well as many other species of Tetra, thrive in the same water conditions. They are peaceful, although they may engage in fin nipping when stressed or in overcrowded tanks.

Guppy: There are many varieties of guppy that make great tank mates. What they all have in common is that they are peaceful fish that are not too small and get along well with everything that will not eat them. Some of the more ornamental varieties add splashes of color to your community tank.

Bristlenose Pleco Variants: A few different color variants will keep well together and may result in interesting-looking varieties through breeding.

Corydoras: Like Plecos, Corydoras are a variety of bottom-feeding catfish commonly placed in tropical freshwater aquariums. They grow up to 4 inches in size and are peaceful omnivores.

Cardinal Tetra: Cardinal Tetras make great neighbors with many kinds of similarly gentle species. A small school of Cardinal Tetra adds beauty to any aquarium and does not create any type of significant bioload to the tank. Always a great choice. Add them in groups of 10.

Neon Tetra: Another great tank mate choice. Adding them in groups of 10, same as Cardinal Tetra, per 20 gallons will give you an ever-moving, shimmering display.

Green Neon Tetra: If you want to keep a brightly colored aquarium, the Green Neon Tetra is another tank mate to consider. Similar in size and appearance to the Neon Tetra, the Green Neon Tetra, as its name implies, has a beautiful streak of neon green along its sides.

Bloodfin Tetra: One of the more colorful species, Bloodfin Tetras are usually in full color and will be more prominent during the day when your rainbow fish have become more muted.

Uaru: This gentle cichlid will not try to eat rainbow fish and makes a good larger tank mate. Give it some rock structure to orient on if you include them.

– Here are some species best avoided as tank mates:

Kissing Gourami: This species of Gourami is a popular aquarium fish because of the kissing motions it uses to both feed and fight. It grows quite a bit larger than the Honey Gourami, up to 12 inches in length, and while quite beautiful, it can be aggressive to smaller fish in all levels of the aquarium.

Paradise Gourami: The Paradise Gourami is a beautifully striped and colored member of the Gourami family that is known both for its appearance and aggressive behavior. They will often fight other fish to the death and should not be placed in aquariums with peaceful species such as rainbow fish.

Cichlids: Aside from Uaru, most members of the cichlid species are too aggressive to do well with rainbow fish. Trying to cohabitate them will lead to bullying and fighting at the least.

Oscars: Members of the Oscar family tend to grow too large, too quickly, and have belligerent attitudes. Small Oscars will badger rainbows, and large Oscars will eat them.


All varieties of the Australian rainbow fish are omnivorous. Small insects and invertebrates, as well as algae, are part of their natural diet.

That makes feeding them quite easy. As insect feeders, they are used to taking food on the surface. Omnivore flakes with a good protein balance are a good all-around choice for them.

A good rule is to give them about 75 percent flake food and 25 percent meaty variety food. Good choices for are frozen and live:

  • Brine shrimp
  • Chopped blood worms
  • Chopped earthworms
  • White worms
  • Feed the fish two to three times each day but limit the feeding time to a few minutes. This will keep food waste from accumulating and will keep your rainbow fish from overeating.


Australian rainbow fish can be readily bred. Because there are so many subspecies of rainbow fish that can interbreed, you should be careful that you are using the same species males and females if you want to try breeding them.

Mixing subspecies often produce fish that are dull or lacking in color.

In the wild, rainbow fish breed during the flood season when the water is cooler and food is plentiful. Setting up these conditions in a separate breeding tank gives you the best chances of successful breeding.

The breeding tank should have a good filter and plenty of bottom vegetation such as java moss to catch the eggs. Some breeders have used yarn spawning mops that can hold eggs.

Rainbow fish are egg scatters. The female will lay her eggs above vegetation, and the males will follow and fertilize them.

To get your rainbow fish in the breeding frame of mind, place several fish with the ratio of two males to four or five females in the breeding tank. Keep the water temperature in the tank at the low end of their comfort zone, about 72 F.

Increase the amount of protein in their food mix, so they are getting mostly meaty proteins such as brine shrimp and chopped blood worms.

As the female rainbow fish becomes gravid with eggs, she will start to puff up, and the male will begin to increase its color intensity.

Watch your fish, especially early in the day when their lights first come on. You may see your males all lit up with colors and females scattering eggs. Once the eggs are fertilized the adult fish are done with them.

Eggs not hidden or caught in vegetation and spawning mops are often eaten by adult fish.

Rainbow fish eggs are very small, and the female will release hundreds at a time. Spawning continues over a few days until the female is out of eggs. That is the best time to remove the fish back to their home tank so the eggs can hatch without being eaten.

The fry will hatch in about a week. Once swimming, they can be fed liquid fry food or infusoria until they are large enough for small chopped foods or omnivore fish flakes.

The fry grow slowly. It takes about two months for them to reach a size where they can be moved to a community or species aquarium.

During the spawning and rearing time, be sure to keep the water very clean for the optimal health of your newborn fish.


  • There are at least 50 varieties of Australian rainbow fish. Keep your school the same species so you do not inadvertently create off-color crossbreeds.
  • The fish you find in stores and online are mostly bred in commercial fish houses in Florida and Asia.
  • Rainbow fish are very active but are also peaceful.
  • They are most active and colorful in the mornings.
  • The minimum aquarium size for keeping a school of 6 is 30 gallons.
  • Keep their water temperature between 74 to 78 F.
  • Rainbow fish can tolerate differences in pH and dH but need fresh, clean water.
  • Use a good quality filter and change part of the water weekly or biweekly.
  • If you attempt to breed rainbow fish, remove the adult fish from the breeding tank after spawning so they do not eat the eggs.
  • Feed your rainbow fish omnivore flakes with meaty protein treats to balance out their diets.

Australian rainbow fish have a very dedicated following around the world. This is a category of fish that may lead you to multiple tanks housing multiple varieties.

It is an ideal fish for dedicated aquarists. With rainbow fish, you will have the opportunity to add your knowledge to the growing body information available to keepers worldwide.

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