Rasbora sarawakensis
The species Rasbora sarawakensis was first described by TR Roberts in 1989. The genus name Rasbora is thought to be derived from the local Bengali name for the fish, Cyprinus rasbora, as described by Hamilton in 1822. However, Bleeker designated R. cephalotaenia as the type of the genus. The specific epithet sarawakensis refers to the state of Sarawak on the island of Borneo, suggesting that the fish originated in this region.
Description
Rasbora sarawakensis has a relatively sturdy and laterally flattened body with a large, pointed head. The base colour of the fish is gold, sometimes with a faint green or silver sheen. The head is usually gold, while the flanks have a striking dark blue longitudinal stripe that runs from the gill covers to the caudal peduncle. Above this stripe runs a lighter orange stripe. The dorsal and caudal fins are translucent red/orange. The ventral, anal and pectoral fins are transparent.
Males are generally slimmer and more intensely colored than females. Females have a more rounded abdomen, especially during the breeding season.
Rasbora sarawakensis can reach a maximum length of about 4-5 cm.
Behavior and Temperament
Rasbora sarawakensis is a peaceful and social fish that is best kept in groups. They are schooling fish and show the most natural behavior when kept in groups of at least 8-10 individuals.
This fish species is peaceful and can live well with other peaceful fish species. They live in schools and usually swim in the middle water layers of the aquarium. They are not shy and show their best colors and behavior when kept in groups.
Lifespan
In a well maintained aquarium these fish can live for about 2-3 years.
Biotope
Rasbora sarawakensis is native to Malaysia and Indonesia. They are endemic to the island of Borneo and are found in the Malaysian state of Sarawak and the Indonesian province of West Kalimantan (Kalimantan Barat). They live in several river systems, including the Batang Kayan, Sungai Sarawak, Mempawah and Melawi.
Habitat
They inhabit slow-moving forest streams with dense vegetation. These streams are often shaded by the dense canopy of the rainforest. There is a lot of underwater vegetation, often consisting of fallen tree branches and leaf litter. The waters are usually clear but have a light brown color due to the tannins that are released from the organic matter that falls into the water.
The edges of the water are covered with trees and dense vegetation, which provides shade and protection. The bottom of these streams usually consists of a thick layer of silt, covered with fallen tree branches and leaf litter.
In their natural habitat, water levels can rise dramatically during heavy rains, indicating periods of flooding. There are no specific reports of droughts, but the variations in water levels suggest a dynamic water level depending on the seasons.
Diet
In the wild, Rasbora sarawakensis feeds on both aquatic and terrestrial invertebrates that fall into the water. This includes small insects, larvae, and other small invertebrates that occur in their natural habitat. They are opportunistic feeders and may also consume ripe wild fruits that fall into the water, although they probably eat the maggots and organisms that live on the rotting fruit.
In an aquarium environment, Rasbora sarawakensis is omnivorous and will accept a wide variety of foods. The diet can consist of: flake and small granules, live foods such as tubifex, mosquito larvae, daphnia, artemia and the like. It is important to vary the diet to ensure that the fish receive all the necessary nutrients and to promote their health and color.
The Aquarium
For keeping Rasbora sarawakensis, an aquarium of at least 80 liters with a minimum length of 60 centimeters is recommended. If you want to keep multiple pairs, it is advisable to use a larger aquarium, for example 100 liters or more, to provide enough space for their social behavior and to reduce stress.
The aquarium should be well planted with fine-leaved aquatic plants and floating plants to provide shade and mimic a natural environment. Adding driftwood and branches will also help to soften the light and create a natural feel.
A dark, soft sandy substrate is best suited for Rasbora sarawakensis. This helps to mimic the natural environment and allows the fish’s colors to stand out better
Water parameters
The best water values for Rasbora sarawakensis in the aquarium are:
- Temperature: 22-26°C
- pH: 6,0-7,5
- Hardness: 2-12° dGH
Suitable Tank Mates
Rasbora sarawakensis can be kept together with other peaceful, small fish species. Suitable tankmates are: Small tetras, rasboras, guppies, mollies, platies, small barbs, corydoras, small peaceful catfish.
Avoid keeping Rasbora sarawakensis with aggressive or predatory fish, as well as fish large enough to view them as prey.
Breeding aquarium and Conditioning
Rasbora sarawakensis is usually bred in a special breeding tank to achieve the best results. This tank must meet specific requirements to ensure successful breeding.
A breeding tank of at least 40-50 litres is suitable for a small breeding group. The water should be soft and slightly acidic, with a pH between 6.0 and 7.0 and a hardness of 2-12° dGH. The lighting should be dim, preferably by using floating plants to dim the light and mimic a natural environment. A soft sponge filter is ideal to create a gentle water flow without disturbing the eggs or young fish.
This is a free-spreading plant that lays its eggs between fine-leaved plants. Place a large tuft of Java moss in the breeding aquarium.
Preparation and Conditioning
The adult fish should be conditioned with high quality live foods such as Tubifex, red, white and black mosquito larvae, as well as artemia. This helps to bring the fish into optimum condition for breeding.
It is often useful to temporarily separate the males and females and then reintroduce them to the breeding tank to encourage breeding. This can increase the willingness to mate.
A breeding group can consist of multiple males and females. A ratio of 1 male to 2 females is often recommended to increase the chance of successful fertilization.
The Spawn
During spawning, the colors of Rasbora sarawakensis become more intense, especially in the males. The males display their most vivid colors to attract the attention of the females. The blue longitudinal stripe and the orange-red fins become more conspicuous, which provides a visual spectacle in the aquarium.
Egg deposition
The eggs are laid on fine-leaved aquatic plants. This provides the eggs with protection and a suitable environment for development. Mating usually takes place in the morning, although this can vary depending on the conditions in the aquarium.
Rasbora sarawakensis is an open-layer, meaning that the eggs are laid openly and exposed among the plants. They show no brood care and the parents must be removed after laying to prevent them from eating the eggs.
Number, Size and Color of Eggs
The number of eggs laid can vary, but it is common for several to occur before a female is exhausted of eggs. The eggs are small and usually transparent or pale yellow in color. They are difficult to see against the background of plants and substrate, which gives them some protection from their own parents.
Raising the fry
The eggs of Rasbora sarawakensis usually hatch after an incubation period of 18 to 48 hours, depending on the temperature. The young fish begin to swim freely about 24 to 48 hours after hatching.
The young fish should initially be fed with Paramecium or similar microorganisms. Once they are large enough, they can be fed with microworms and Artemia nauplii.
Conclusion
Rasbora sarawakensis is a peaceful and colorful fish that is suitable for both beginners and experienced aquarists. They require a well-planted aquarium with a dark sandy substrate and dim lighting. They can live well with other peaceful, small fish species and are easy to feed with a varied diet. They do not show parental care and should be kept in groups to promote their natural behavior.
Video
Author
John de Lange
Copyright images
Choy Heng Wah
AquariumGlaser.com
