Boeseman’s Rainbowfish 101: Care, Diet, Tank Size, Tank Mates & More

If you’re like most people, you probably think of rainbows as being those colorful arcs that show up in the sky after it rains. But did you know that there are actually fish that are called rainbows? One of these is the Boeseman’s Rainbowfish.

Not only are they lively and fun, but they’re also one of the most durable fish species. And the best part? The Boeseman’s Rainbowfish is not just one color, but six different shades of red, orange, yellow, blue, purple, and green that change with their moods and surroundings. 

So if you want a lively display in your tank, take a few minutes to read this guide.

Species Summary

Boeseman's Rainbowfish
Boeseman’s Rainbowfish

Boeseman’s Rainbowfish is a species of tropical freshwater tetra belonging to the Melanotaeniidae family. These tetras are found in Asia and endemic to Lake Ayamaru in Irian Jaya, Indonesia. The species inhabits a reduced area and are commonly found amid vegetation.

They are known for their bright colors and active personalities. But the secret to getting beautiful colors is to offer quality feed. Their must be varied, and, more importantly, the aquarist must carry out frequent water changes in the aquarium.

These Rainbowfish reach an ideal size to be kept in an aquarium and exhibit a beautiful behavior when in a large shoal, causing an extraordinary impact on the viewer. They are highly sought-after fish for their unique beauty, especially the red dot (“heart”) located on their sides, which gives their common name.

When looking at an adult male, it is easy to see why they are called a bicolor rainbow fish. These animals have a beautiful grayish blue on the front half of their body and a vibrant orange-red on the other half.

Boeseman’s Rainbowfish Care Guide

These fish are very hardy and can live in community aquariums with other fish without problems. This species has gregarious habits like other rainbows, so you should always keep them in schools. When well cared for, the Boeseman’s Rainbow is a beautiful fish, but they will show their best colors when given a balanced diet and in a suitable aquarium.

Whether you’re thinking of getting a Boeseman’s Rainbowfish, or you already have one, this guide will teach you everything you need to know about their care.

Tank Size

Boeseman’s Rainbowfish are relatively small, only reaching a maximum size of about 3 inches. Even though they are small, they still need a lot of space to swim and feel comfortable. It is recommended that you keep them in an aquarium that is at least 21 gallons, with dimensions starting at 31″ x 11″ x 15″. This size will accommodate a small group of fish well, but always remember that the more space you can give them, the better.

Tank Mates

Boeseman’s Rainbowfish are beautiful, peaceful fish that makes a great addition to any community aquarium. They are easy to care for and get along well with other fish, making them a great choice for both beginners and experienced fishkeepers alike.

While they are generally peaceful, Boeseman’s Rainbowfish can sometimes be aggressive or shy with certain tankmates. It’s important to do your research before adding them to your tank to make sure they will get along. Persecutions between members of the same species may also occur, a natural behavior related to group hierarchy.

Boeseman’s Rainbowfish have small mouths, so they do well with small tankmates like shrimp. Other good choices include Danios, Corydoras, Tetras, other Rainbows, Rift Lake Cichlids, and Barbs.

Same Species Tanks

The Boeseman’s Rainbow is often kept as a single species in large aquariums, planted tanks, or biotope-type aquariums where the species’ original location is mimicked.

It is a great species to be kept alone in a well-decorated aquarium. A shoal forms many beautiful movements and a beautiful color explosion. 

Water Parameters

They are very resistant fish, which means they can tolerate a wide range of water parameters, including those that are on the alkaline side. However, they are susceptible to pollutants in the water and the accumulation of organic matter in the tank. They also do not do well in soft or acidic water.

The ideal temperature for keeping Boeseman’s Rainbowfish is between 78 and 86 degrees Fahrenheit, and the ideal pH range is between 7.0 and 8.0. The hardness of the water should be between 9 and 19.

What to Put in Their Tank

If you’re thinking of adding a Boeseman’s Rainbowfish to your tank, there are a few things you need to know to make sure they thrive.

First, you’ll need a heater and a filter. The filter should be sized appropriately for the tank and create a moderate flow. You’ll also need a lid, as these fish are known for jumping.

Second, keep in mind that these fish need a lot of space to swim. Even if your tank is densely planted, make sure there’s plenty of open space for them to move around.

Third, Boeseman’s Rainbowfish are best kept in groups. They are social creatures and will do best when they have other fish to interact with.

By following these simple tips, you can create a happy and healthy environment for your Boeseman’s Rainbowfish.

Additionally, the aquarium’s decoration is not critical to guaranteeing success in maintaining the species, but it is incredibly beneficial to have a tank that mimics the conditions of the biotope. Fine sand as substrates, with some driftwood and a lot of plants, is an excellent way to go. 

Make sure that the tank is well decorated and forms hiding places and territories. Boeseman’s Rainbowfish tend to go very well in densely planted aquariums. The larger the shoal, the more natural its behavior and color enhancement.

Common Diseases

Boeseman’s Rainbowfish are remarkably disease-resistant fish. However, like all fish, they can fall prey to common environmental conditions such as acidosis. 

Acidosis is a condition caused by high acidity in the water and can be deadly if not treated quickly. The best way to prevent acidosis is to maintain a stable pH in your tank. 

Likewise, these fish are easily susceptible to environmental stress. This is usually caused by poor water quality and can be fatal if not treated quickly. The best way to prevent environmental stress is to keep your tank clean and your water quality high.

Food and Diet

These fish are omnivorous, meaning they will eat both plants and animals. Their wild diet consists of micro-crustaceans, worms, and plant matter. The availability of food in their natural habitat dictates what they will eat.

In an aquarium, these fish will readily accept all types of food. A good diet for them includes high-quality commercial feed and live, fresh, or frozen foods such as bloodworms, brine shrimp, or daphnia. Feeding them a varied and balanced diet is essential for them to reach their full potential.

It is important to set a time to feed these fish, as they are always hungry. They should be fed an amount that can be consumed quickly.


In nature, these animals are prone to live less, as they are predisposed to diseases, attacks from other animals, and environmental causes. But if you provide them with a good home and take care of them, you can expect them to stick around for a long while. In an aquarium with all the correct parameters kept stable and with an ideal diet, this animal can live for more than 6 years, with the most common being around 5 years.


Boeseman’s Rainbowfish are well-known for their beautiful colors and patterns. But what does this fish look like? 

Boeseman’s Rainbowfish have an oval-shaped body with the caudal peduncle (the part of the body that the tail is attached to) projecting from the back. Their fins are not large, but the fins on the top and bottom of the fish stand out, following the animal’s outline. 

Also, their head is narrow, presenting themselves as a continued flattening of their body. This fish has relatively large eyes and a small mouth, giving the species a unique appearance.

As for their coloring, each half of the body exhibits a color. Most Boesemani Rainbowfish have shades like reds, oranges, and yellows on the back, with more fabulous shades of blues, purples, and greens on the front. The colors vary according to physiological and environmental factors, which are more intense when the fish is healthy.


The Boeseman’s Rainbow can quickly grow to 4.3 inches in length when well cared for and fed, but the everyday sight is around 3 inches.

Behavior and Temperament

Boeseman’s Rainbowfish are incredibly active animals and love to occupy the middle and upper parts of the tank. However, they’re also surface-feeders, so they’ll often be seen in the middle part of the tank as well. Their behavior is much more natural when they’re kept in a group of at least six individuals – if you keep them in pairs or trios, there may be some persecution of the weakest fish in the group.

Their behavior can change if they don’t feel comfortable in the tank. They may become stressed if they’re hidden among vegetation, rocks, and driftwood – some even call it “depression.” However, when they’re left alone, they’ll often become much more active and engaged.

These peaceful fish love to spend their time vying for territory or the attention of females. Males will often face each other and display their fins and colors in the most impressive way possible. 


Captive breeding is doable and is carried out commercially and even accidentally in home aquariums worldwide. However, the fry can be a little tricky to raise.

It is an oviparous species, where the female freely spawn the eggs in the middle (egg-scattering species) and do not exhibit parental care. The female releases her eggs into the water, usually near the bottom, leaves, or rocks. 

The male immediately swims around the eggs, fertilizing them. The fry hatch in 7 to 12 days, depending on the temperature. A few days after hatching, the fry has consumed the yolk sac contents and begins to swim freely.

In practical terms, the breeding tank should be at least 10 inches long. The water should be alkaline and slightly hard. The pH should be around 7.5, and the temperature should be within the ideal range for the species.

Overall, they are easily reproduced fish, where spontaneous reproduction can occur in any domestic aquarium, as long as it is well taken care of.

Gender Differences: Male vs Female

One of the most distinguishing features of Rainbowfish is the sexual dimorphism between males and females. Adult males are larger and have more intense coloration, and the dorsal fin rays are more elongated. 

Females have a broad mid-lateral dark band accompanied by corresponding narrow yellow or reddish-orange longitudinal stripes that can darken or lighten according to their mood. In addition, mature females often show similar coloration to betta males but are usually easily identified by their smaller and rounded fin edges.

Boeseman’s Rainbowfish Fun facts

● It is by far the most popular rainbow fish in the aquarium hobby, and most of the specimens found in stores come from farms in the Far East and Eastern Europe. As they mature, they present an increasingly striking color, usually from twelve months of age, being one of the most attractive species available on the market.

● Its biotope, even comprising a small area, undergoes extreme variations in parameters. In the wettest months (April and June), the lake can rise to 5 meters from its usual dry season level. Water parameters can change significantly according to the location and time of year. According to Vries, lakes and streams have a pH ranging from 6.4 to 7.8, while Heiko Bleher reported opposite conditions with a pH close to 9.0. When Marinus Boeseman collected his specimens, he registered a pH of 6.4-6.5.

● It has a remarkable resemblance to M. ajamaruensis. Still, the latter has a thinner body, and the first dorsal fin is positioned more forward (near the middle of the eye) than M. boesemani.


Allen, G.R., 1991. Field guide to the freshwater fishes of New Guinea. Publication, no. 9. 268 p. Christensen Research Institute, Madang, Papua New Guinea.

ASAP, Aquarium Science Association of the Philippines, 1996. Aquarium species in the Philippines. ASAP Aquarist Database Report. 9 p. Quezon City, Philippines.

Hilton-Taylor, C., 2000. 2000 IUCN red list of threatened species. IUCN, Gland, Switzerland and Cambridge, UK. xviii + 61 p.

Humphrey, C, D.W. Klumpp and R. Pearson, 2003. Early development and growth of the eastern rainbowfish, Melanotaenia splendida splendida (Peters). I. Morphogenesis and ontogeny. Mar. Freshwat. Res. 54:17-25.

Home of The Rainbowfish – National Library of Australia.