Boeseman’s Rainbow – Melanotaenia boesemani

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Frequently overlooked by aquarists as a boring fish, nothing could be further from the truth! M. boesemani are active and beautiful, and in the presence of a shoaling group display wonderful, active, mating rituals.

Scientific Name: Melanotaenia boesemani (Order: Atheriniformes, Family: Melanotaeniidae)

Common Names: Boeseman’s Rainbow, Boesemani Rainbow, Boeseman’s Rainbowfish

Discovered: Allen and Cross (1980)

Region: Papua New Guinea

Maximum Size: 9 cm (not counting tail)

pH Range: Near neutral (6.5-7.5)

Hardness: 9-19 dH

Temperature: 76-82 F (24-28 C)

Appearance: Heavily age-dependent. Young are white/translucent with little color and a stream-lined, minnow-like body (they resemble Pseudomugil spp. adults strongly). Juveniles are elliptically shaped with bright orange posterior half and shimmering luminescent silver/blue anterior half. Full adults are deep-bodied and almost triangular/rectangular. They have solid orange posterior halves and almost-solid blue or silver anterior halves.

Environment: Freshwater lakes in New Guinea. Lake Ajamaru region and Lake Aitinjo, further south.

Feeding Habits: Omnivorous. Will accept flake or pellet. A high quality food such as New Life Spectrum or Omega 1 is recommended, as these provide the fish with important pigments.

Distinguishing Sex: Males are larger than females (9 cm. max vs. 7 cm max). Females always have a lesser coloration, and are almost unrecognizable as M. boesemani when young. Females’ bodies tend to be less deep when fully mature. Females develop orange color later. Behaviorally, females are more docile, and males more active. Males display finnage more frequently than females.

Behavior: Benthopelagic. The fish are highly active. Males will display constantly for the females, demonstrating some of the most spectacular finnage of any fresh-water fish. They will school loosely, more so if they feel threatened.

Breeding: Rainbows are mop spawners, and shouldn’t be considered “parents” in the sense that most cichlids are. Conditioning should be done in the following way. Allow a large group of the fish to mingle in a medium-sized tank. Then separate a pair off and isolate them in a smaller aquarium with java moss or an artificial green-dyed “mop” of yarn. Females will be holding eggs, and males will fertilize externally. The young are very small, so must be fed rotifers and infusoria until able to accept flake food.

Lifespan: 5+ years.

Advice on Purchasing: I have frequently found sick-looking specimens of these and other rainbowfish in the store. My advice to you is not to buy young specimens (under 1.5″) and certainly not to buy olders specimens with shrunken-looking stomachs, irregular-looking scales, cottony mouths, heavy breathing. These are all problems I’ve noticed with a lot of LFS rainbowfish, and they’re hard to treat if you do get the fish (I lost a lot of Praecox Rainbowfish to this mysterious disease).

This is another fish I feel strongly about. As they are less colorful when young, they are frequently overlooked by aquarists as a boring fish. Nothing could be further from the truth! M. boesemani are active and beautiful, and in the presence of a shoaling group display wonderful, active, mating rituals.

Sadly, these fish are endangered and on the IUCN endangered species list. Their availability, nonetheless, is due primarily to the fact that several breeders in the US keep them circulating in fish stores. Their rarity causes them to be a much sought-after item, but it also inflates their price. Most juveniles are $8-12, and full adults go for $25 or potentially a great deal more. These are not particularly difficult to breed, so the market for them will probably increase in the future, and their price will decrease accordingly.

I bought my first M. boesemani about 5 months ago, and have since bought 9 more juveniles. I plan to try and mate them in the future, but all but the first are too young still. I have experienced nothing but joy from these fish. They are so active and full of personality that I almost prefer their behavior to that of cichlids! My relatively-mature specimen is the center of my 55 gallon, and always gets a comment or two from friends. His color stuns—his tail is a wonderful orange, but his anterior half shimmers with many different colors, his dorsal fin is rimmed with white, and his anal fin is garnished with pink.

I recommend that aquarists take an active role in attempting to keep and breed this fish. As its range in the wild is so limited, it will probably never become as omnipresent as certain other species, but it has a great potential to win over the hearts of many aquarists in the future. Keep them and care for them! This is a wonderful species of fish!

If you’re interested in getting some first generation (F1) juveniles, consider rarefishatlax on Tanner has HQ fish with provenance, and many other species of similar rainbows for your consideration.

My Rankings:
Price: 6 (usually $9+)
Value: 10 (always worth it)
Hardiness: 9 (require clean water)
Community: 10 (absolutely fine)
Activeness: 10 (males are always displaying!)
Appearance: 10 (fantastic color)
Overall: 10 (worth it!)


• Helfman, Gene, et al: The Diversity of Fishes. Malden, MA: Blackwell Science, 2003.

• Hemdal, Jay F: Aquarium Fish Breeding. New York: Barrons, 2003.

Last update: 2006-02-06 09:52
Author: madasafish

Filed under Fish Profiles, Freshwater.