Species Snapshot
- Species Name: Melanotaenia praecox
- Common Names: Dwarf neon rainbowfish
- Size: Up to 3 inches
- Lifespan: 3-5 years
- Native Distribution: New Guinea, Indonesia
Covered in iridescent blue scales, the dwarf neon rainbowfish is a sight to behold. This diminutive rainbow fish species is an excellent fit for freshwater community tanks—especially planted tanks where their color will be shown to its best advantage.
If you’re considering adding dwarf neon rainbowfish to your tank, here’s everything you need to know to care for them properly.
Anatomy and Appearance
The dwarf rainbowfish (Melanotaenia praecox) belongs to the subfamily Melanotaeniinae of rainbowfish. This singular species is known by many names including the neon rainbowfish, dwarf neon rainbowfish, diamond rainbowfish, and Praecox rainbowfish. This species gets its nickname from its small size—it grows only to an average length of around 3 inches at maturity.
Like other Melanotaeniidae species, this rainbowfish exhibits a laterally compressed body that is rounded in the middle but tapers at either end. What makes rainbowfish particularly easy to identify is their dorsal fins run almost the length of the fish’s body with barely noticeable separation between the two. Their scales are also fairly large, compared to other fish, and have a noticeably iridescent sheen.
Dwarf neon rainbowfish have silver bodies. In the right light, however, they shine an iridescent blue. All the fins are rimmed in red-orange, most vibrantly in males of the species. Females are a little less colorful overall, having less blue in their body color and more of a yellow hue in their fins.
Ideal Aquarium Setup
Though dwarf neon rainbowfish are fairly small, they’re a fast-swimming species so they need plenty of open swimming space along the length of the tank. For this reason, long rather than tall tanks are recommended. It’s also best to replicate the tropical elements of their natural habitat, including plenty of live plants.
Tank Size
Because dwarf neon rainbowfish are schooling fish, they should be kept in groups of at least six of the same species. A small group requires a minimum tank size of at least 20 gallons, though larger tanks are always preferred. Be sure to scale up the tank size if you plan to keep this species along with other community fish.
Water Parameters
The dwarf neon rainbowfish is endemic to one of the largest river systems on the island of New Guinea in Indonesia. The Mamberamo River system flows swiftly, so fish like the dwarf neon rainbowfish prefer to have a little flow in the tank. It’s also important to keep water quality high with a strong filtration system and regular water changes.
In terms of water chemistry, this species prefers warm, slightly alkaline water—even better if it’s on the hard side. The ideal temperature range for these fish is 74°F-80°F and they prefer a pH between 6.8 and 7.5. Dwarf neon rainbowfish are adaptable to a range of pH and GH levels but the ideal water hardness level is 5-15 dGH.
Tank Décor
Planted tanks are best for dwarf neon rainbowfish but it’s important to strike the right balance between giving your fish places to hide and offering plenty of swimming space. Tall plants like Vallisneria work well because they move with the current and the leaves are easy to swim amongst. Floating plants will also be welcome, considering these rainbowfish don’t like bright lighting—floating plants will help diffuse the light coming from above.
Other than live plants, decorate your rainbowfish tank with other natural elements like driftwood and rocks. Use plants and natural elements to create alternating areas of open space and décor. This may help cut down on squabbles between males in the group.
Diet and Feeding
Dwarf neon rainbowfish are omnivorous and tend not to be picky eaters. They’ll generally accept a wide range of commercial foods including flakes, granules, and pellets. If you want your fish to achieve their most vibrant color, be sure to offer live, frozen, or freeze-dried foods from time to time. Brine shrimp, bloodworms, and tubifex worms are great options.
Temperament and Tank Mates
For the most part, dwarf neon rainbowfish are a peaceful species that does well in community tanks with other similarly sized fish. Because they’re fast swimmers, they may even be compatible with slightly larger or semi-aggressive species. Just avoid keeping them with any fish large enough or aggressive enough to eat them.
The best tank mates for these rainbowfish are other small schooling or shoaling species like danios, barbs, and characins. This species will get along with other rainbowfish and some docile cichlids like dwarf cichlids. Don’t be afraid to include bottom-dwellers in your rainbowfish tank, either. Corydoras catfish and freshwater gobies will do just fine.
Breeding Dwarf Neon Rainbow Fish
Once they’re mature, dwarf neon rainbowfish are fairly easy to sex by comparison. Males tend to be larger and more brightly colored than females—they also develop more depth in their body shape as they mature.
Dwarf neon rainbowfish are egg scatterers, so they’re not particularly difficult to breed in the home aquarium. The fry, however, can be a little tricky to raise to maturity. It’s best to spawn your rainbowfish in a separate breeding tank at least 18 inches long. The water should be slightly hard and alkaline but the pH close to neutral.
Fill your breeding tank with fine-leaved plants like java moss for your rainbowfish to scatter their eggs amongst. Once the rainbowfish are conditioned in the main tank, move the plumpest female and the most brightly colored male into the breeding tank to spawn. If they need a little encouragement, a slight rise in tank temperature might do the trick.
Dwarf neon rainbowfish often spawn several times a day over weeks. Because the adults tend to eat their eggs and fry, having plants or a spawning mop to give the young cover is essential. You may also want to monitor your fish closely and remove the adults after spawning. The eggs will hatch after 7-10 days and will require very small foods, like infusoria until they get large enough to eat powdered food or baby brine shrimp.
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