"Brunei Beauty"

Adults grow to 9–10 cm. Males are larger and display a rich red coloration with black markings on the head and fins. Their fin edges and tips have white borders. Females look different; their colours are less vibrant, usually grey, with faint horizontal stripes running from head to tail.

This fish comes from Southeast Asia, specifically the island of Borneo (Kalimantan), where it inhabits the northern parts of the Malaysian state of Sarawak and the adjacent nation of Brunei Darussalam. Its limited natural range is heavily affected by human activity, which has led to a substantial decline in population numbers. At present, Betta macrostoma is among species on the brink of extinction. Despite an export ban on endangered species imposed in Brunei, Sarawak has no such restrictions, which sometimes allows wild-caught specimens to be obtained. The "Brunei Beauty" inhabits the headwaters of small streams and fast-flowing rivers with clear water in tropical forests. Dense vegetation keeps sunlight from reaching the water surface, creating conditions of constant twilight. The substrate is rocky and sandy, with a small amount of organic debris such as leaves and branches. Aquatic plants grow mainly along the banks.

This is a highly temperamental fish. Intraspecific relationships are based on the dominance of an alpha male over subordinate individuals, determined through fighting that sometimes escalates into ritualized contests. Even among females there is a hierarchy, and conflicts sometimes occur. In a small tank it is best to keep only one pair. Aggression towards other species has not been observed. In fact, large and active fish may intimidate the "Brunei Beauty" and exclude it from food sources. It is compatible with peaceful species of comparable size.

For one or two fish, an aquarium of 80 litres or more is optimal. When setting up a tank for the "Brunei Beauty", recreate conditions close to its natural environment. Use gravel or sand substrate, treated natural driftwood, and shade-loving plants such as:

• Cryptocoryne
• Thai fern
• Java moss
• Bucephalandra

Leaves from certain trees, pre-soaked and placed on the bottom, make a useful addition. These leaves serve both as decoration and help create the chemical composition of water characteristic of the species' natural habitat, as they release tannins as they decompose. Maintain high water quality through continuous operation of the equipment, especially the filter, and regular tank maintenance. This includes weekly water changes with fresh water matching the pH, GH and temperature, prompt removal of organic waste such as uneaten food and faeces, and other routine procedures.

In its natural habitat, this fish feeds on small invertebrates, zooplankton and freshwater shrimp. Newly acquired fish may initially refuse unfamiliar foods, but acclimated individuals or offspring of wild-caught specimens readily accept the dry, frozen and live foods common in the hobby. Specially formulated feeds for Betta fighting fish are recommended.

The main difficulty in breeding lies in finding a compatible pair. If, for example, you acquire a male and female from different sources and place them together, peaceful coexistence is unlikely, and in some cases the weaker individual may even die. For successful spawning, the fish must grow together. Spawning is preceded by lengthy courtship, during which the male and female perform a characteristic "embrace dance", pressing closely against each other. At this moment the eggs are fertilized, and the male immediately collects them in his mouth. The incubation period, during which the eggs remain in the male's mouth, lasts from 14 to 35 days. The fry that emerge are fairly large (around 5 mm) and are already able to accept microfood such as brine shrimp nauplii or specialized foods for young aquarium fish.

Most health problems in fish often arise from unsuitable keeping conditions. Maintaining a stable and comfortable environment is key to successful care. If disease symptoms appear, first check the water quality. If problems are found, take immediate steps to correct them. If symptoms persist or worsen, medical treatment may be needed.

When selecting fish, pay attention to their activity and the absence of fin or scale damage. A healthy fish should show curiosity, have clear eyes and even breathing without signs of rapid gill movement. Avoid purchasing specimens showing signs of starvation, a sunken belly, or unnatural coating on the body. Note that this species often displays intraspecific aggression, so when buying a group at the shop, carefully observe their behaviour in the display tank. If possible, it is preferable to acquire an already-formed pair, as pairing fish from different batches can lead to serious conflicts and injuries.