Aquarium for Melanotaenia.
They inhabit fresh and brackish waters of Australia and New Guinea. Peaceful, active, schooling, and jumpy fish. What unites them all is a love for clean, flowing, brackish, slightly alkaline water and bright sunlight. Generally peaceful, rainbowfish can live in a community aquarium with any calm neighbors. Small Pseudomugilidae and Iriatherina need a species-specific aquarium with dense thickets because they are very timid fish and cannot live together with large Melanotaenia, Glossolepis, and Chilatherina.
The depth of the aquarium is not as important as its length and width, especially for larger species. An aquarium well-planted with fine-leaved plants, with open swimming areas, where plants are not disturbed. Rainbowfish love dense vegetation in aquariums; near the ends and the back wall, there should be plant shelters, branching driftwood, and tall stones, while the front part should have open swimming space. Rainbowfish are excellent jumpers, so the aquarium should be carefully covered. Peaceful, schooling, and mobile fish, they mostly stay in the upper layer of water.
Most of these fish live in the tropical and subtropical climates of Australia and New Guinea. Since they live in schools in their natural habitat, they should be kept in spacious aquariums with 4-8 individuals of the same species together. In large aquariums, the fish grow larger than their wild counterparts, becoming very deep-bodied and colorful. Depending on the type of lamps used, the coloration of the same individual can change significantly. They treat each other peacefully and pose no threat to other inhabitants.
In a community aquarium, Melanotaenia are best kept with medium-sized related species, barbs, large danios, Epalzeorhynchus, Aplocheilus, and livebearing fish. They are great for a community aquarium with not-too-aggressive neighbors. They are ideally suited for co-habitation with medium-sized Malawi and Tanganyika cichlids, calming them down with their schooling behavior, as well as with livebearing toothcarps.
Since the fish spend most of their time in the middle and upper parts of the aquarium volume, you should consider stocking the bottom. Any bottom-dwelling fish can get along here — catfish, gobies, loaches, Pangio, spiny eels, small non-aggressive Lamprologus, Julidochromis, and Telmatochromis. Bottom-dwelling fish are also useful because they eat food that has fallen to the bottom. After all, rainbowfish feed mainly in the water column or from the surface and rarely go down to the bottom.
Rainbowfish will eat any fish food you give them, but this does not mean that every food is good for them. A key element of this fish species’ health is that they must receive food that they eat in their natural habitat. The jaws of Melanotaenia are so densely studded with teeth in the front that there is no doubt about their diet — these fish consume a fair amount of filamentous algae. In the wild, Rainbowfish feed mainly on algae, small plants, and may also eat aquatic and terrestrial insects, tadpoles, crustaceans, and very small fish.
However, the majority of their diet consists of algae. Even high-quality dry fish food is not quite the right choice for feeding these small fish, because the composition of most dry foods is designed for omnivorous fish that eat more “meat” than plant matter. Such a diet, rich in protein and lacking (or very low in) plant fiber, puts Rainbowfish at risk of various health problems. Fish deprived of plant food, especially with a monotonous diet, will receive food unbalanced in amino acids, which ends up in health disorders, poor coloration, and emaciation.
Many aquarists feed Rainbowfish a protein-rich diet because it increases their growth rate. But it is worth noting that an accelerated growth rate does not indicate fish health. Most importantly, your fish should look healthy and happy, but this type of food actually creates a risk of health problems. In nature, Rainbowfish also feed on various insects, crustaceans, and even small fish. This means that some percentage of “meat” food is simply necessary for them. The “meat” portion of your Rainbowfish’s diet should be 35-40%. Fatty foods should be avoided. Monotonous, heavy feeding with bloodworms or tubifex causes toxicosis and dropsy.
In an aquarium, certain water quality factors are very important, such as the level of nitrogen compounds, dissolved oxygen, pH, and temperature. When keeping rainbowfish, it is advisable to use external filters, as the water must be very clean, free of suspended particles, and low in nitrogen compounds. The water must have one primary quality — containing as little protein breakdown products as possible, which poison Melanotaenia. They prefer hard or medium-hard water with a slightly alkaline reaction. It is necessary that the water in the aquarium does not stagnate, ensuring active movement of water masses. Regular water testing is essential and helps identify problems before your fish get sick.
They are sensitive to low oxygen levels; aeration, filtration, and water changes (up to 30% weekly) are required. The addition of table salt or sea salt to the water has a positive effect on fish health, with a salinity of 2-5% when necessary. Constant water temperature should be around 22-27 degrees, hardness level 7-25, acidity 6.3-8.0, salinity 2-5%. They live for 3-6 years.
Aquarium with Cyprinid fish. Rasboras, Devario, and Danios. 
