For a fish that measures less than 25mm in length, Dwarf Rasbora (Boraras maculatus) have huge personalities. These fish are very peaceful but are not suited to the general community aquarium due to their small size and rather timid nature. As such, Dwarf Rasbora are best kept in a dedicated species tank. Although this fish can be housed with other species, they need to be chosen with care, as larger, more aggressive or boisterous fish will cause the Dwarf Rasbora to spend most of their time hiding.
Suitable compatible species include; Sundadanio, Danionella, Microdevario, Eirmotus, Trigonostigma, Pygmy Corydoras and Otocinclus. Dwarf Rasbora also make ideal companions for members of the genus Sphaerichthys (See: Chocolate Gourami) and Parosphromenus.
Most sources recommend keeping Dwarf Rasbora in schools of at least 8-12 individuals, however, I have found them to be a lot more active when kept in greater numbers. In groups smaller than 12 the fish become reclusive and tend to venture off on their own, rather than forming a school. I would recommend keeping a group of between 16 and 20 individuals. The larger the school, the more colourful and interactive these fish will be.
Dwarf Rasbora originate from South Eastern Asia where they are found in Peninsular Malaysia, Thailand and Singapore. They are widely distributed throughout Peninsular Malaysia, while the other countries have more limited populations. While different populations may differ in colouration and patterning, these differences are small.
In the wild, Dwarf Rasbora inhabit small, gently-flowing black water streams, often associated with peat swamps. These streams are often bordered by thick marginal vegetation and overhanging trees, which means that very little light penetrates the water’s surface. Overhanging vegetation also results in streams being littered with fallen leaves and branches, the decomposition of which results in the release of tannins and other humic substances, which stain the water brown. The water in these streams is usually very soft and acidic and Dwarf Rasbora are often found in areas that have a pH-value as low as 4.0.
Fortunately for hobbyists, we do not have to replicate these water parameters in the home aquarium. As long as the water is soft, lower than 5° of hardness, and below 7 pH, these fish will thrive. Although Dwarf Rasbora are easy to keep when kept in the right conditions, they are sensitive to changes in water chemistry and should never be introduced to a biologically-immature aquarium. It is important therefore that the tank is well established before adding this fish.
Aquarium & Care
Although Dwarf Rasbora can be housed in rather small aquariums, their requirement for low nitrate levels makes them best suited to slightly larger aquaria. An aquarium with base dimensions of 45 cm by 30cm is large enough for a school, although larger base dimensions will be appreciated by the fish. Dwarf Rasbora are best kept in a densely-planted aquarium, as this gives them ample space to hide and promotes the growth of microbe colonies, which the fish are able to feed on. They also make an excellent addition to the carefully aqua-scaped setup, as their bright red colouration contrasts well with the green of the plants.
Fairly dim lighting should be used to simulate the conditions this fish would encounter in nature. The addition of some floating plants and roots or branches to diffuse the light entering also seems to be appreciated and adds a more natural feel.
As this fish comes from slow-moving streams, filtration should not be too strong, as the Dwarf Rasbora may struggle if the current is too fast.
The substrate should consist of dark, soft sand as this best simulates the natural environment from which this fish originates.
The addition of dried leaf litter further emphasises the natural feel and encourages the growth of microbe colonies which can provide a valuable food source for fry. The tannins and other humic substances released by the decaying leaves are thought to be beneficial to these fish. Leaves can be left in the tank to break down fully or removed and replaced every few weeks.
These fish often look dull and unattractive in dealer’s tanks but know this, that once you bring them home they will quickly colour up, provided they are kept in the right conditions. So the next time you see these fish in a dealer’s tank, take the time to consider keeping them. Those who decide to try their hand at keeping these tiny fish will be richly rewarded.