Profile Photo

Maximum size : 5 cm

Blue Line Rasbora - Rasbora sarawakensis : Complete Fish Profile & Care Guide

Table of contents


Despite being uncommon in the aquarium trade, the Blue Line Rasbora is a sociable and attractive fish. In a peaceful community of Southeast Asian or Indian species such as Rasboras, Barbs, Loaches and Gouramis, this species should fit in perfectly. There should be at least eight to ten Blue Line Rasboras in a group as they are a naturally schooling species. It will make the fish less nervous and result in a more effective, natural display if they are kept in decent numbers. When males compete with one another for female attention, they will also display their best colours. Rasboras usually show better colouration when kept in a well-planted tank with a dark substrate, but the choice of decor is not very important. To add a more natural feel to the aquarium, some floating plants and driftwood roots or branches are appreciated. Because these fish come from sluggish waters, the filter does not need to be particularly strong. Blue Line Rasboras have a large, pointed head and a relatively stout body. An orange longitudinal stripe and golden ground colour distinguish it from other species.

Blue Line Rasbora Photos

Sexual Dimorphism

It is quite simple to differentiate between the male and female Blue Line Rasbora. The females are usually less colourful, are generally larger and are plumper than the males. In contrast, the males are slimmer, smaller, and more vibrantly coloured than the females.

Quick Facts

Scientific NameRasbora sarawakensis
Year Described1951
Other NamesSarawak Rasbora
Max Size5 cm
Aquarium LevelMiddle - Top
DifficultyBeginner - Intermediate
Best kept asGroups 10+
Lifespan3 - 5 years

Water Parameters

Water TypeFreshwater
PH6.0 - 7.5
GH2 - 12
72 - 78
22.2 - 25.6

Natural habitat

Both the Malaysian state of Sarawak and the Indonesian province of Kalimantan Barat are home to the Blue Line Rasbora. Many river systems in Sarawak and Kalimantan Barat contain them, including Batang Kayan, Sungai Sarawak, and Mempawah. Usually living within the shade of rainforest canopy, these Rasboras inhabit sluggish flowing streams with dense emergent vegetation. Silt and fallen tree limbs cover the bed of these streams, which are typically covered in a thick layer of silt. This results in relatively clear water in their habitats. As organic matter decomposes in the stream, it releases tannins that turn it pale brown.

How to breed the Blue Line Rasbora

It is uncertain if the Blue Line Rasbora has been bred in the hobby, although it should be possible. These Rasboras are continuous spawners that scatter eggs and do not care for their young. However, the fish will spawn frequently when in good health, and small numbers of fry may begin to appear without human intervention in a densely-planted, established aquarium. It is necessary to take a slightly more controlled approach if you want to increase the yield of the fry. In addition to conditioning the adult group together, one or more containers should also be set up and half-filled with water. It is recommended that these be dimly lit and that the bottom is covered with a mesh large enough to allow the eggs to fall through but small enough to prevent the adults from getting to them. You can also use artificial grass matting, which works well. There should be a slight acidity to neutrality in the water and a slight temperature increase. Power filters can be added to the aquarium, with the flow going down its length. It is best to introduce one or two pairs of adult fish to each container after the females appear full of eggs and the adults are well-conditioned. Then, by gradually topping up the aquarium with cool water and feeding small amounts of live and frozen foods, spawning can be initiated. It is likely that a female will spawn several times before she runs out of eggs. To prevent babies from being sucked up by the power filter, you should switch the power filter to a mature sponge filter after a couple of days. Incubation usually takes 18 to 48 hours, and the young are free-swimming within 24 to 48 hours after hatching. Initially, the fry should be fed Paramecium or similar food, then microworms and brine shrimp once they are large enough to accept them.

Diet & feeding

In the home aquarium, the Blue Line Rasbora will readily accept most good quality dried foods such as granules, flakes and sinking pellets. These modern food products have been developed to provide all adequate nutrition to maintain your fish's health and dietary requirements. Providing additional foodstuffs such as live, frozen, and freeze-dried meals such as bloodworm, daphnia, and tubifex once or twice a week will provide other benefits to your fish's health and well-being but is not a must for this fish. It should be noted that bloodworms should only be given as an occasional treat and should not be used as the staple diet as they are difficult for fish to digest and can potentially cause blockages. This fish is an omnivore in the wild, meaning it will consume some vegetable matter. Although most modern fish foods take this into account and include them in their products, you can still supplement your fish's diet with blanched vegetables such as spinach, broccoli, and zucchini. Ensure you do not overfeed your fish and remove any leftovers the following day.

Other Rasboras you maybe interested in