Rasboras are schooling fish in the family Cyprinidae, which means they’re related to barbs, danios, goldfish and koi. They are peaceful, colorful fish, and most species grow to less than 4 inches, making them ideal for small to mid-size aquariums. Popular species like harlequin, lambchop, scissortail, lampeye (eyespot) and brilliant (also called redtail or black line) rasboras typically don’t get larger than 2 inches. They are active and hardy, making them good beginner fish for 10 gallon aquariums or larger. Smaller species such as dwarf emerald rasboras and various species of Boraras are relatively new to the aquarium hobby. Most of these brilliantly colored fish max out at 1 inch or less and are perfect inhabitants for desktop and nano aquariums of 3 to 10 gallons. Rasboras are schooling fish, so they’re best purchased in groups of 7 or more, although groups of 25 or more are a sight to behold!
A Rasboras Natural Habitat
Rasboras are found throughout south and southeast Asia, including southeast China. They mostly inhabit gently flowing forest streams, but also occur in floodplains during the wet season. They prefer shallow water and abundant aquatic plant growth. The water is often stained brown from tannins released by leaves and other organic matter, and the pH can be as low as 4.0 in some habitats. Light is often subdued due to overhanging vegetation.
Water Requirements for Rasboras
While some rasboras, especially members of the genus Boraras, are collected in the wild where the water is very soft and slightly acidic, the majority of aquarium species sold today are raised commercially in water with higher pH and alkalinity than their native environment. For these fish, pH should be between 6.8 and 7.8, alkalinity between 3° and 8° dkH (50 ppm to 140 ppm), and temperature between 75° and 80° F. If the aquarium is kept in rooms below 75°, use an Aqueon® aquarium heater to increase the heat. Wild-caught fish prefer a pH of 5.0 to 7.0 and KH between 1°and 3° (20 ppm to 50 ppm). Maintain good filtration and change 10% to 25% of the water weekly to twice a month using an Aqueon® Aquarium Water Changer or Siphon Vacuum Gravel Cleaner. Don’t forget to treat tap water with Aqueon® Water Conditioner before refilling your aquarium!
Housing Requirements for Rasboras
Rasboras are happiest in a well planted aquarium and they do best in groups of 7 or more. They will be less stressed and show their best colors in a well decorated aquarium with dark substrate. The filter should provide a gentle current to simulate the slow-moving streams they live in in nature. Keep a secure lid on the aquarium to prevent them from jumping out.
Rasboras are peaceful and most species get along well with similarly sized community fish. Depending on species, they can be housed with other rasboras, small tetras, croaking, sparkling and chocolate gouramis, celestial danios, pentazona barbs, guppies and platies. Suitable bottom dwellers include otocinclus, kuhli and other small peaceful loaches, and corydoras catfish. Dwarf rasboras such as those in the genus Boraras are best kept in a species tank, but due to their small size, they are one of the few fish species that can also be housed with freshwater shrimp. Always consult an aquarium expert before buying any new fish for your aquarium.
What do Rasboras Eat?
Most rasboras are considered micropredators, meaning they feed on small insects, zooplankton, worms and tiny crustaceans in nature. They will thrive on Aqueon® Tropical Flakes, Color Flakes, Tropical Granules and Shrimp Pellets. For extremely small species, crush dried foods to match their mouth size. Frozen and live foods can also be fed as treats or to help induce spawning. For best results, rotate their diet daily and feed only what they can consume in 2 to 3 minutes, once or twice a day.
Rasboras Breeding Level – Difficult
Most rasbora species kept by aquarists are egg scatterers that distribute their eggs among plants and provide no parental care. Harlequin, lambchop and a few other species are known to attach their eggs to the underside of plant leaves. Healthy adult fish kept in mature well-planted aquariums will sometimes produce young with no assistance from the aquarium owner.