Boraras maculatus

The Dwarf Rasbora is a true gem for small aquariums, often called the Pygmy or Spotted Rasbora. This tiny fish, originating from Asia, showcases a beautiful reddish-orange body, especially in males, accented by a distinct dark spot on its side. Its colors truly shine when it feels safe and happy in a well-maintained environment.

These are shy and peaceful creatures that must be kept in a group. A lone Dwarf Rasbora will feel stressed and spend its time hiding, but in a school, they become more confident and display fascinating social behaviors. They prefer a tank with gentle water movement and plenty of live plants, driftwood, and leaf litter to explore and hide in, which mimics their natural habitat and makes them feel secure. Dimmer lighting is often preferred and helps to bring out their vibrant coloration.

Due to their tiny size and peaceful nature, they are best kept in a species-only tank or with other very small, calm inhabitants like shrimp or other nano fish. Avoid any tank mates that are large, boisterous, or aggressive, as the Dwarf Rasbora will be easily intimidated and outcompeted for food. Feeding them is straightforward, but remember their mouths are minuscule. They require finely crushed flakes, micro-pellets, or small live and frozen foods like baby brine shrimp to thrive.

For the dedicated hobbyist, keeping Boraras maculatus is an exercise in creating a specialized micro-habitat. Success with this species hinges on replicating the blackwater peat swamps of Southeast Asia. This is achieved by creating soft, acidic water conditions, ideally using reverse osmosis (RO) water remineralized to a low TDS. The introduction of botanicals like catappa (Indian almond) leaves, alder cones, and peat granules in the filter is highly recommended. These elements release tannins and humic acids, which lower the pH naturally and stain the water a transparent tea color. This stained water is not 'dirty'; it is the key to unlocking the species' best health, most intense coloration, and natural behaviors, while also providing valuable antimicrobial properties.

The social dynamics within a school are captivating. In a well-established group in a suitable environment, males will engage in ritualistic sparring. This involves them flaring their fins and displaying their most brilliant red hues to each other to establish a social hierarchy. This is a dazzling spectacle, not a violent confrontation. To further bolster their confidence, consider the use of 'dither fish'—another small, peaceful, and slightly more outgoing species that signals the environment is safe, encouraging the rasboras to swim more openly in the middle and upper water columns.

Breeding Boraras maculatus is a rewarding challenge. They are continuous egg-scatterers, showing no parental care and will predate their own eggs. For successful breeding, a dedicated setup is almost essential. This tank should have very soft, acidic water and be densely packed with fine-leaved plants like Java moss or provided with synthetic spawning mops. The fish can be conditioned on a rich diet of live and frozen foods like daphnia and microworms. After a few days of spawning activity, the parents must be removed. The resulting fry are incredibly small and will require microscopic first foods such as infusoria or commercially available liquid fry food before they are large enough to accept newly hatched brine shrimp. Careful attention to water quality is paramount during this delicate rearing phase.

Boraras maculatus, a member of the Danionidae family, is a diminutive cyprinid native to the peat swamp forests and associated blackwater streams of Southeast Asia, including Malaysia, Sumatra, and Borneo. Its generic name, Boraras, is an anagram of Rasbora, a deliberate choice by the describers to highlight its status as one of the smallest members of the group. The specific epithet, maculatus, is Latin for 'spotted,' a direct reference to the prominent, dark, circular blotch situated mid-laterally on the fish's flank.

Morphologically, the species exhibits a fusiform, laterally compressed body typical of small, active cyprinids. Sexual dimorphism is pronounced. Males are generally more slender, smaller in overall size, and display intense reddish-orange pigmentation across their body and fins, which becomes significantly more vibrant during periods of social display or reproductive activity. Females are comparatively larger, possess a rounder abdominal profile, and exhibit a more subdued, yellowish-tan base coloration. In addition to the primary lateral blotch, smaller, less distinct dark markings can often be found at the base of the dorsal, anal, and caudal fins, with their intensity varying between populations and individuals.

Ecologically, B. maculatus is a specialized inhabitant of extreme blackwater environments. These habitats are characterized by very low water conductivity, negligible carbonate hardness, and a highly acidic pH, often falling below 4.0 due to the high concentration of tannins and humic acids leached from decaying plant material. Within this biotope, it functions as a micropredator, foraging in the middle to upper water column for zooplankton, small insect larvae, worms, and ostracods. Its reproductive strategy involves continuous fractional spawning, wherein small batches of adhesive eggs are scattered amongst fine-leaved aquatic vegetation (e.g., Cryptocoryne species, Java moss) on a daily basis. This lack of parental care is a common trait among cyprinids in such environments. The specific water chemistry is a critical trigger for spawning and is vital for preventing fungal and bacterial infections on the developing eggs.