The Rasbora's are not a huge group of fish in the fish keeping trade, but they include a few of the most popular and well-known species available to hobbyists today.
In addition to the well known species there are new rasbora's appearing continually in shops, and many make great little aquarium fish for the increasingly popular planted aquariums, smaller tanks, and softer water aquariums.
The Rasbora's (Rasborinae) are part of the larger group of carp-like fishes (Cyprinidae), which includes barbs, sharks, and loaches. Danios are also part of the Rasbora group, although these are covered in another article.
Virtually all rasbora's originate from Southeast Asia and Indonesia although their local habitats vary from small pools and heavily vegetated streams to high altitude rivers and flowing waterways. Few are found in larger rivers and their small size makes them much more suited to smaller environments where they are less likely to be preyed upon by larger species.
Rasbora's are all micro-predators, meaning they feed primarily on tiny aquatic organisms and insects, which are often in abundance around smaller waterways and vegetated areas.
Rasbora's will spawn in the right environment but to successfully raise fry a special breeding tank must be set-up with equipment and decor designed specifically for the purpose of raising fry. Since the parents are generally small fish anyway, the fry are particularly tiny and need to be fed on liquid foods or rotifers for the first stages of their lives.
Rasbora's are egg layers and depending on the species will either scatter eggs or lay eggs amongst or on plant leaves. Thick areas of vegetation are required for spawning by most species and the addition of floating plants will also help. Many rasbora species can be encouraged to spawn through the use of very soft, slightly acidic water, plenty of vegetation and some natural sunlight combined with shaded areas. Courtship displays by males are common and pairing may take place several days before spawning.
A few rasbora's, such as the White Cloud Mountain Minnow, and some of the larger species are undemanding of their aquarium environment. Other species, particularly the smaller rasbora's, will only stay in top condition if kept in quite specific surroundings.
Planting is important for these fish, and dense areas of vegetation are appreciated as hiding spots and hunting grounds. Bright light will only be tolerated if shaded areas are available as retreats, so some floating plants are a good addition.
Filtration should not be too strong and although water quality is important, water changes should be kept small since the fish appreciate a mature environment. Being natural micro-predators, a varied diet is important to keep top health and dried foods should be supplemented with smaller frozen or live foods such as daphnia, Cyclops, and small brineshrimp.
The rasbora's are all peaceful grouping species with good natures and make great additions to smaller communities. Whilst activity amongst other fish should not pose a problem, any species that are likely to be boisterous, aggressive, or intimidating should be avoided.
Since most rasbora's are quite small, only small non-predatory species will make good tankmates. Small barbs and tetras, Corydoras, dwarf species of gourami and shrimps are all good tankmates for rasbora's and suit their preferred aquarium style of planted aquariums well.
Of all the rasbora's, the White Cloud Mountain Minnow (Tanichthys albonubes
) is by far the most well known. As the name suggests, the fish originates from the 'White Cloud Mountain' in southern China and because it is a high altitude fish, cooler temperatures are preferred.
The white cloud minnow's origin is also responsible for its popularity; fishes which come from higher altitudes are usually found at the beginning stages of rivers, and these parts of a rivers life are heavily prone to fluctuations in water conditions and temperature caused by seasonal changes and even daily weather systems. In the aquarium environment this translates to a fish that is hardy and tolerant of changing conditions.
The distinction to make when keeping these fish is between the words 'tolerate' and 'live comfortably'. Because a fish is tolerant and does not die under sub-standard conditions, does not mean it is happy or should be kept in such a way.
Like Goldfish and Siamese Fighting Fish, White Clouds are often seen kept in aquariums far too small and with no filtration, which can only be considered cruel by any real fish keeper. However, these are adaptable and robust little fish, which will thrive in a proper aquarium environment, can be kept in unheated tanks, and are peaceful with all other species, making them an excellent aquarium fish.
Virtually all White Clouds seen for sale are now captive bred and a number of selective variations are available including albino and long-fin varieties as well as several varieties with differing colours.
The Harlequin Rasbora (Rasbora heteromorpha
) is a long-standing aquarium fish in the trade and has a striking and well-defined dark patch on the rear half of the body, combined with a strong purple-orange body colour. These are shoaling fish, although adults will shoal less, but still prefer to be kept in groups. When young the fish can look a little weak and lethargic but as they gain size they become deeper bodied and more robust in appearance.
Fully grown harlequins, at around 4-5cm, can even be kept with significantly larger peaceful fish in planted aquaria. There are several similar species of rasbora that look and behave like harlequins including the Narrow Wedge Harlequin (Rasbora espei) and the Slender Harlequin (Rasbora hengeli). Both these fish are slightly smaller and more slender than the Harlequin, and all three species can be mixed together.
Other small species
There are many small species of rasbora, and with new fish arriving on import lists continually, many of these appear for a period in aquatic stores before being replaced by something different in a few months. One of the mainstays is the Pygmy or Dwarf Rasbora (Boraras maculatus
), a tiny little fish that grows to no more than an inch and is one of the smallest known fishes. The Pygmy Rasbora has an intense brown-red colour interspersed with a couple of dark spots and makes an excellent fish for heavily planted displays where groups will dart in and out of the vegetation.
As with other small fish, regular feeds and a varied diet are important for maintaining good health. In the wild these types of fish regularly pick at tiny food items throughout the day. With such tiny digestive systems, the fish can only eat small amounts at one time and if only given foods once a day, they may quickly become malnourished.
Not all rasbora's are tiny species, and many grow to a reasonable size for community aquariums. The Scissor-Tail (Rasbora trilineata
) is a well-known and popular aquarium fish, and growing to 15cm it can be kept with many larger species. Like other rasbora's, these are shoaling fish and must be kept in groups otherwise their timid nature will result in stress and ill health without the safety of a group. Scissor Tails are not the most colourful of fish, with a plain silvery body but their name comes from the yellow and black markings on the tail which when moved, create a 'scissor-action' movement. It is the active nature and visual displays of movement that attracts the observer to these fish in the aquarium.
Other common larger rasbora's include the Elegant, or Two-Spot Rasbora (Rasbora elegans), a peaceful, shoaling grey-silver fish that reaches up to 20cm and the Clown Rasbora (Rasbora kalochroma), which looks very similar to the Pygmy Rasbora, but grows up to 10cm.
The larger rasbora's also appreciate planted areas but will spend more time out in the open, so open swimming spaces should be provided. Whether large or small species, the rasbora's are almost all very peaceful shoaling fish, which adapt well to aquariums with a little vegetation and peaceful tank-mates. As an alternative to tetras, of which some can be nippy, and barbs, of which some can be boisterous, the rasbora's fill this niche very nicely indeed.