Chocolate gourami

The chocolate gourami (Sphaerichthys osphromenoides) is a uniquely fascinating anabantoid native to blackwater peat swamps and associated streams of the Malay Peninsula, Sumatra, and Borneo. Its deep chocolate-brown body is crossed by several thin, golden-yellow vertical bars, creating a subtle but elegant colour pattern unlike any other labyrinth fish. It reaches a standard length of 4–5 cm and is distinguished within the genus by having 9–10 dorsal fin rays and a reduced or absent light bar anterior to the dorsal fin. The species is also remarkable among anabantoids for its unusual reproductive strategy: it is a maternal mouthbrooder — one of only two Sphaerichthys species in which the female broods the eggs and fry in her mouth for 7–20 days before releasing fully-formed, free-swimming juveniles.

Chocolate gouramis are slow-moving and timid, requiring carefully selected tankmates. They are easily intimidated and outcompeted for food by larger or more boisterous species. Small, peaceful cyprinids such as Danionella, Microdevario, Trigonostigma, and smaller Rasboras make excellent companions, as do Pangio loaches. Though not schooling in the traditional sense, they are gregarious and should be maintained in groups of at least 6 individuals; groups develop noticeable social hierarchies and display more natural behaviour when kept in numbers. In nature they are chiefly micropredators feeding on small aquatic crustaceans, worms, insect larvae, and zooplankton. In the aquarium they can be picky and may initially refuse dried foods, so a consistent offering of small live and frozen fare such as Artemia nauplii, Daphnia, and grindal worm is essential.

An aquarium with base dimensions of at least 60 × 30 cm (roughly 54 litres) is suitable for a small group. The most important requirement is soft, acidic water mimicking blackwater conditions: a sandy substrate, plenty of driftwood roots and branches creating shaded caves, and dried leaf litter (beech, oak, or Ketapang almond) to stain the water with tannins. Filtration should be gentle, and large water changes avoided — weekly changes of 10–15% are adequate. Recommended water parameters include a temperature of 26–31°C, pH 4.0–6.5, and hardness near zero (0–54 ppm) for wild specimens, though tank-raised individuals are more adaptable. The aquarium must have a tightly-fitting cover as the labyrinth organ requires access to warm, humid air above the water surface.