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Quick Overview:

  • Family: Melanotaeniidae
  • Scientific Name: Melanotaeniidae
  • Care level: Easy
  • Temperament: Peaceful and non-aggressive
  • Diet: Omnivorous
  • Water conditions: Alkaline, warm waters
  • Max Size: Six inches
  • Recommended tank size: 55 gallons

Rainbowfish Care: Overview

Once you’ve seen a rainbowfish, you won’t have any confusion as to how it got its name. These brightly colored species are a blast to raise and offer fish hobbyists a once-in-a-lifetime opportunity. These fish co-habitat well with dozens of other fish species, exhibiting tranquil personalities and docile behaviors. An attractive addition to any aquarium, these fish are unique in that their iridescent coloring allows them to seemingly change shades in different lighting.

These freshwater species originated in Southeast Asia and Australia and can tolerate of most living conditions. As a schooling fish, they prefer to be housed with other fish, making them a good choice for a fish hobbyist with other groups of fish. These fish can live up to ten years in some cases, making them a good choice for committed aquarium owners.

Rainbowfish Appearance

Rainbowfish have a unique appearance, with males and mature fish sporting more vibrant colors than their younger or female counterparts. Juveniles will often have drastically different coloring from adults, often looking like other species altogether. Females are usually a bit smaller than males, and will also be duller in color.

What size are they when they’re small?

As babies, rainbowfish are usually less than an inch in length. They are dull in color and often look nothing like their adult counterparts. They are considered fully grown, depending on the species, once they have reached about a year or two in age.

How fast/slow should you expect them to grow?

Rainbowfish will grow rapidly within the first few months of life, but their growth will drop off and slow once they have reached about an inch and a half. Those who reach maximum size – six inches or more – are generally of a species with genetics to support more rapid growth, and these individuals often grow to be very old by the time they reach their maximum size.

What’s their max size?

As an adult, a rainbowfish can be anywhere between one to six or more inches in length. This depends on the species. In the wild, rainbowfish often do not grow to maturity, as they are threatened by factors such as habitat destruction and over-2harvesting.

Different Types of Rainbowfish

There are about sixty-one different known species of Rainbowfish, with most varieties living well in captivity. Therefore, if you say you own a rainbowfish, you’re not being very specific – each type of rainbowfish is radically different from the next, meaning you can have an entire aquarium filled with rainbowfish that look nothing alike.

  • Threadfin Rainbowfish
  • Salmon Red Rainbowfish
  • Blue Eyes
  • Sepik Rainbowfish
  • Boeseman’s Rainbowfish
  • Banded Rainbowfish
  • Australian Rainbowfish
  • Parkinson’s Rainbowfish
  • Dwarf Neon Rainbowfish
  • Lake Kutubu Rainbowfish

Rainbowfish – Diet & Feeding

What do rainbowfish eat in the wild?

In the wild, rainbowfish are omnivores. They will eat both plant and animal matter. Rainbowfish prefer to eat food that floats on the surface of the water in the wild, such as water insects or floating vegetation. Here is some great food to feed your Rainbowfish with!

Rainbowfish Feeding Habits

Rainbowfish are primarily surface feeders, meaning they feed on the top couple of layers of the water column. As a result, you need to make sure you feed them frequently, but in small doses. Any uneaten food will rapidly sink to the tank’s bottom, compromising your water quality and the overall health of your fish.

The best foods to feed rainbowfish are those that comprise both vegetable and meat sources. Consider feeding them color or spirulina flakes, or even betta treat or tropical flakes. They may also require some live foods in order to promote good health. You can feed them solely commercial flake food, but throwing in occasional ground vegetables or frozen shrimp is also a good idea.

As a special treat, you might even consider purchasing mosquito larvae, as this comprises a large portion of their diet in the wild. Other potential treats include blackworms, bloodworms, or glassworms.

What foods are recommended for rainbowfish?

Whichever foods you choose, consider rotating out your fish’s diet every few days. This will allow them great variety and higher levels of nutrition than if you feed the same foods every single day. Floating flakes are preferred, as this mimics their natural feeding patterns.

Only feed them what they can consume in less than two minutes, as the rest will either spoil or result in overfeeding. You can feed your fish up to three times a day, but don’t feed too much at a time. Try to avoid foods that are exclusive to one food group, and always thaw any frozen food before feeding it.

Rainbowfish Tank Setup

Brief overview of natural habitat

Rainbowfish are native to Australia, Indonesia, and Papua New Guinea. Here, they are found in abundance in the warm waters of streams, lakes, rivers, and even swamps.  They prefer waters that are somewhat hard and alkaline. Unfortunately, the natural habitat of rainbowfish is being threatened, as more invasive species are introduced to the waters.

Furthermore, human activity such as logging and overfishing has drastically reduced their populations in the wild. These fish are still frequently farmed commercially in places such as Southeast Asia and Florida. Rainbowfish are very active in the wild as well as in captivity.

Tank size (and why this much space is needed)

Rainbowfish need plenty of room to swim. Depending on the subspecies you select, you will need anywhere between 30 and 55 gallons to keep them happy. They tend to hang out on the middle to upper levels of the water. While the ideal tank size for rainbowfish can vary, it’s important to note that perfect water quality, temperature, and pH are vital for maintaining happy, healthy rainbowfish.

Rainbowfish are very active and should be given plenty of space to swim around. Planted tanks are ideal, as some species will nibble on soft-leaved plants but otherwise leave them alone.

Now, while most rainbowfish prefer larger tank sizes, you can keep them in small aquariums if you are willing to compromise on the exact species of rainbowfish you decide to raise. A ten-gallon tank can hold up to fifteen rainbowfishes, as long as you select smaller species such as Pygmy or Dwarf rainbowfishes. Larger groups can be housed in larger tanks, while smaller groups of larger species will have to make do in average-sized spaces.

Water conditions (Temperature, pH, KH)

Although rainbowfish are typically raised in alkaline waters, commercially bred fish can tolerate a wide range of water conditions. They adapt easily to a variety of living conditions, with some subspecies of rainbowfish adapting to certain conditions and water quality levels more easily. That being said, they prefer temperatures between 74 and 78 degrees Fahrenheit, generally with a pH of around 7.0 to 8.0 and alkalinity that rests somewhere between 5 and 20 dKH (or 90 to 360 parts per million).

If your aquarium is kept in a room that falls below 74 degrees Fahrenheit, consider using a tank heater to increase the temperature. Make sure you use an adequate filtration unit and swap the water out every two weeks with treated tap water. Consider checking the water temperature and filter daily to make sure everything is normal, and always introduce new rainbowfish to the new tank very gradually, and not in a hurried fashion.


It’s important to provide rainbowfish with plenty of decorations and places to hide. Consider using tall plants or other structures to ornate the tank. That being said, don’t overdo it with the decorations. Rainbowfish need plenty of open swimming areas, which will mimic their natural environment. Adding decorations, however, can help reduce the stress levels of your fish by making them feel more secure and giving them places to hide.

Artificial plants can be used in the tank, as can live plants. Whichever option you choose, try to provide a variety of colors and leaf shapes to make your tank look more appealing to both you as well as the fish who will ultimately live in it. Good choices of plants include Java mass and Java fern, for example. These types of plants may also provide good spawning sites for rainbowfish, as they do in the wild. Bogwood, rocks, and other decorations can also be used, but again, make sure you leave plenty of open swimming space.

Rainbow fish from genus Melanotaenia in an aquarium.

Rainbowfish Tank Mates

General Behavior

Rainbowfish are known for being placid, non-aggressive species. Some subspecies of rainbowfish are known for their shoaling behaviors and should be kept in groups of six or more for best results. It’s interesting to watch rainbowfish in large groups, as the males will display bright shows of color in order to attract attention.

Despite this unique behavior, rainbowfish are mostly shy, and will not confront larger, more aggressive species when threatened. They prefer to hide, ducking behind plants and rocks when they feel stressed. Although your fish are unlikely to fight with each other, you should take proper care to make sure stress is minimal in their lives, as this can increase their susceptibility to disease and reduce their overall quality of life and longevity.

Rainbowfish Tank Mates

Because rainbowfish are so easygoing, they can be kept with a number of other species, both small and large. Keep in mind that male rainbowfish will often fight if there are not enough females to go around during the breeding season. Therefore, it’s advised to keep your female to male ratio slightly off-balanced, so that there are always more females than males.

What follows is a list of the fish species with which rainbowfish cohabitate well, although the list is by no means exclusive. Rainbowfish can live with most other fish species, provided that they are active and consume a similar diet (which helps reduce the likelihood of tank pollution due to wasted food).

  • Non-aggressive cichlids (such as Kribensis)
  • Danios
  • Catfish
  • Barbs
  • Large tetras
  • Rasboras
  • Caridina shrimp
  • Neocaridina

How to Keep Rainbowfish Healthy

Common diseases to look out for

Common signs of disease in rainbowfish include a loss of color (or a new sort of overall dullness), spots of fungus on the mouth or body, uneven breathing, or a lack of movement. Because rainbowfish are so active, a fish that suddenly appears to be lackadaisical or listless is likely sick.

Fin rot is one of the most common diseases in rainbowfish. This is displayed in the form of frayed fins, usually with reddened bases. This is generally caused by poor water quality and can be treated by a veterinarian.

Another common disease, especially among fish living in close quarters, is ich. Rainbowfish who have picked up ich will have white spots on their bodies and fins. They will also display odd behaviors, such as rubbing against hard objects or decorations and swimming erratically. This can be treated by quarantining any infected fish and applying a commercial ich remedy for about two weeks.

Tips on keeping rainbowfish in good health

A healthy rainbowfish will look similar in appearance to those of other healthy species, sporting clear eyes, a healthy appetite, and intact, undamaged fins. They will also hide often, a contrast to other species who prefer to be out in the open when they are in good health. Rainbowfish are easily stressed by overcrowded conditions as well as poor water quality, so staying on top of these two factors can help keep your fish in tip-top shape.

Breeding Rainbowfish

Luckily rainbowfish aren’t that difficult to breed. They are known as “egg scatterers,” meaning they will provide next to no parental care once their eggs have been laid.

That being said, if you want to breed your rainbowfish, consider raising the temperature of your tank. this will increase spawning activity. Rainbowfish will court early in the morning and spawn at first light under ideal circumstances. Before breeding, feed your rainbowfish a varied diet twice a day.

Then, insert a spawning mop (a green cotton thread attached to a cork that dangles in the tank). Check the mop every day for opaque spheres, which should be dotted all around the wool threads. Then, remove the mop and put it into a bare-bottomed aquarium with identical water conditions. The eggs will eventually hatch inside this tank.

The eggs will hatch in one to three weeks, depending on the species and the temperature of your tank, among other conditions.  Rainbowfish can also be crossbred with other species, but the young often appear discolored or stunted. These fish often breed recklessly with other species, producing interesting, somewhat appealing, looking offspring.

Interesting Facts About Rainbowfish

Rainbowfish spawn year-round in their natural environment, contributing to healthy populations if you decide to breed them at home. These fish rarely get sick and are extremely hardy.

Interestingly, rainbowfish were discovered quite some time ago, back in 1843. Early explorers called these fish sunfish, although that term today is used for a number of other freshwater fish species.

Despite their beautiful coloring and their adaptive personalities that allow them to cohabitate well with other species, rainbowfish remains one of the least popular options purchased at pet stores. if this sounds odd, consider the rainbowfish’s appearance in its youth. Young rainbowfish are often not nearly as brightly colored as other fish species, and certainly not as vibrant as adult rainbowfish. Therefore, it’s important for you to consider how your rainbowfish will look when it reaches maturity, instead of how it looks during its juvenile stage.

Is a Rainbowfish Right For You?

Headed out to the pet store? Consider picking up a rainbowfish. They might seem bland at first sight, but that’s only because you’re looking at the juveniles of the species. Rest assured, your rainbowfish will soon mature into an elegant, vibrantly colored individual.

With a docile disposition and a gorgeous appearance – as well as very little work required to maintain one! – a rainbowfish is a great fish to consider for any aquarium owner, whether you are experienced or just starting out in your fish-rearing pursuits.


Hi, my name is Jordan. I've been in the fishkeeping hobby since my childhood. Welcome to my blog where I help fishkeepers enjoy the hobby by offering free guides, advice, & product reviews. Read more...