By Jason Shaw
Campbell River Aquarium Club, British Columbia, Canada
Aquarticles

Common Name: Dwarf  Neon Rainbow Fish
Scientific Name: Melanotaenia  praecox
Wild Distribution:  New Guinea
Length: Up to 2.5 inches
Water Temperature:  75 – 83f degrees

The Dwarf Neon Rainbow Fish is a fairly new addition to the rainbowfish collection.  It was discovered in New Guinea and smuggled to North America in the early 90s.  These guys are just a pleasure to watch. The colours of these rainbowfish reflect beautifully in the light. They are an excellent addition to the community tank since they are very peaceful and like to school with any fish.  

Males differ from females in colour and shape. Males (like the one pictured above) have a red trim on dorsal, tail and anal fins.  The body shimmers with blue and silver.  The males become much deeper body wise and the head may look more pinched.  Females stay slimmer but do get a lot wider when carrying eggs. The females have more of a reddish yellow trim on their fins and the upper body is not quite as shimmery as the males.  They are monstrous eaters - their eating habits are on the disorder side.  I wish I could eat like them!  They seem to prefer surface food, but will chase food to mid level.

Breeding Notes

I was introduced to these little guys in the fall of 2000.  I hadn’t seen much of them before, but took an instant liking.  I’ve tried two different methods of propagation.  They both worked, but one method was much easier:

My brood stock consisted of two males and four females.  Another good ratio would be one male and three females. I constructed a basket, which hung to the sides of a 33-gallon tank. The basket should be at least 15 inches long and 10 inches deep, with the width just fitting inside the main tank.  These fish like their space.  I siliconed a plastic grating to the bottom of the basket;  holes should be 5 or 6 mm in diameter.  I then stuck some old plastic plants to the grating,  just to give them some spawning media.  I had a pH of  6.9 to 7 and my hardness was 2 – 3 degrees.  The water temperature moved between 78 and 80f.

I introduced my breeders to the basket and started on a feeding regime. I always fed in small amounts to avoid food  falling past the grates. Their diet consisted of bloodworms, adult brine shrimp, finely chopped beef heart and spirulina flakes.

Within a few days the females became swollen with eggs. The dominant male then enticed the female around the spawning media. Each female would only release 20 – 35 eggs, but continued to do so every two to four days. The eggs are sticky and sometimes attached by a tiny thread. 

The fry appeared within eight to ten days, free swimming at the surface.  At this point they were ready to be fed. They were very tiny at first and were too small to accept baby brine shrimp. They also stayed at the surface and that’s where they liked to eat.  A.P.R. by O.S.I. seemed to work the best, and “E” type baby fish food by Tetra Min also worked.  Once the fry were two weeks old, they would take microworms and the following week would accept baby brine shrimp.

The fry are slow to start, but once they reach the one-month mark, look out!!!   You should be able to sex your fish at about 2½ months.  Using this method you will be able to harvest 20 – 30 fry every three days.  Move the fry to a smaller tank and keep no more than two weeks’ worth of fry together in the same tank.  If the parents are well fed, they will ignore their young.

The basket method has proven itself.  You can leave the parents alone and harvest the fry as they appear.  Just be sure to keep the tank bottom clean and your brood stock well fed.