Category: Rainbowfish

All about Rainbowfish.

The Madagascar Rainbow

Bedotia geayi is a native of Madagascar where it inhabits fast-flowing mountain waters. While not as elaborately colored as many of the rainbows from Australia and New Guinea, it maintains a pleasing contrast of red, black, and gold. The male has two black stripes running parallel to the lateral line, one running from the mouth through the eye to the beginning of the caudal fin and the other lower on the body running from the throat to the back of the anal fin. As well, the caudal fin has a crescent of black circling the outside of the caudal fin leaving the fin lobes a bright red. The split dorsal fin and anal fin are beautifully edged in black and red but the most vibrant coloration is seen in the back portion of the dorsal fin and in the anal fin which are an almost iridescent blend of gold and orange. The female has only the black markings with a small amount of red edging in the tail.

When I obtained my six fish in the fall of 1995 they were about 25 mm long and just beginning to develop some red coloration. Initially I thought I had four females and two males but as the fish matured, it became clear that there were four males and two females. Not having an empty tank that I could devote to the Madagascar rainbows, I put them in a 60-liter tank with six Melanotaenia maccullochi. The tank was heavily planted with Cryptocorynes that allowed the fish open space above the plants for swimming. A sponge filter with heavy air flow was used for filtration and a green nylon spawning mop held up with a cork was present, initially for the spawning activities of the M. maccullochi.

The fish were active and grew rapidly on a diet of brine shrimp, flake food, and occasionally, white worms. They are horrible mooches, always coming to the front of the tank begging for food as though they haven’t eaten in a week, making it difficult not to overfeed. Water changes of 50% were done about every 10 days as this species is sensitive to water quality. Standard Calgary tap water with a pH of 7.6 and hardness of 240 ppm suites them quite well.

When the fish were only about 30 mm total length, I began to find eggs in the mop. The eggs were quite large for rainbowfish eggs; about 1.5 mm in diameter in comparison to the M. maccullochi eggs which were not quite 1 mm in diameter. Unlike Melanotaenia maccullochi or M. boesemani which may deposit 50 to 100 eggs a day in the mop, the Madagascar rainbows laid only five to ten eggs a day. Presently, the fish vary from 50 mm to 75 mm in length and the egg production is about the same. I have not seen them picking at the mop to eat eggs but it is a possibility, although the reference books claim that they ignore the eggs and fry. I stopped gathering eggs after having accumulated about 60 and have never seen fry in the tank and so am reasonably certain that they do eat fry. When I check the mop occasionally, there is only one day’s worth of eggs in the mop indicating that the eggs are also being eaten.

The eggs were picked from the mop and placed in a margarine container with fresh tap water. The eggs are very robust and may be handled without damaging them. Methylene blue was not necessary as very few eggs were infertile. Eyes were visible in two to three days and the fry hatched in about nine days. The fry are very large compared to most rainbowfish fry and swim at a slightly head-up angle for the first day or two. The fry are able to eat brine shrimp nauplii as a first food, which makes then exceptionally easy to raise. I transferred the fry from the margarine container to a 20-liter tank equipped with a corner box filter filled with carbon between two layers of filter floss. A clump of Java moss was pulled apart to create a loose web and pushed down so that the upper third of the tank was available for swimming. The fry grew rapidly on twice daily feedings of brine shrimp and when they reached 12 mm in size it was necessary to supplement with flake food, as they would eat all my brine shrimp and more! Now, at just under two month of age, the fry are 25 mm total length and red is beginning to develop on the caudal fins of the oldest males.

As the fry got bigger and began to outgrow the 20-liter tank, I decided to put a few in the tank with the adults to avoid overcrowding. I was surprised when the adults killed two of the fry even though they were over 1 cm long. Interestingly, some M. maccullochi fry of the same size that were also introduced were unmolested. I rescued the frantic Bedotia fry and transferred all the fry to a 60-liter tank set up similarly to the 20-liter rearing tank and all are doing well.

Few fishes from Madagascar are available to hobbyists. Here is a species that is colorful, active, easy to maintain, and easy to breed. In fact, I would recommend this fish to a beginning fish breeder for both the ease of inducing spawning and the ease of raising the fry. With the status in nature of Bedotia geayi rated as threatened, we should all make an effort to keep this fish from slipping away. I assure you that this species will repay your efforts with its beauty.


“All About Tropical Fish,” D. McInerny and G. Gerard, Harrap Limited, London, Fourth Edition 1989.

“Baensch Aquarium Atlas 1,” R. Riehl and H. Baensch, MERGUS-Verlag Hans A. Baensch, 1986.

“Aquarium Fish Breeding,” Ines Scheurmann, Barron’s Educational Series, Inc. 1989.

“The Complete Aquarium Encyclopedia,” J. D. Van Ramshortst (Editor), Elsevier Publishing Projects, 1978. ?