Ravnaki's Halfbeak

Ravnaki's halfbeak is a close relative of various Nomorhamphus liemi and Nomorhamphus snijdersi. They share similar colouration, which can lead to confusion in shipments when one species is sold under another's name. This rarely causes problems because both species have identical keeping requirements. The body of Nomorhamphus ravnaki is elongated and somewhat compressed laterally. The jaws are long and pike-like, with the upper jaw shorter than the lower. Males grow to about 6 cm, while females may reach 12 cm. The colour is usually grey with a silvery belly. It differs from related species in fin colouration: the caudal, dorsal and anal fins are reddish with a thin black edge. Another feature of Ravnaki's halfbeak is the red lower jaw and the absence of the characteristic hook-like projection.

This fish comes from the island of Sulawesi (Celebes) in Indonesia, located in Southeast Asia. Its natural habitats are numerous streams and rivers flowing through hilly terrain, mainly on the island's south-eastern side.

Males of this species are noticeably aggressive towards each other, leading to fierce fights, especially in confined spaces. If reliable shelters are present in the tank, the weaker male may use them for protection, but this does not prevent conflicts. In a small tank, keep only one male Ravnaki's halfbeak with 3–4 females. Females are peaceful by contrast and coexist comfortably in a group. The aggression of Ravnaki's halfbeak is directed only at members of its own and closely related species. This fish lives well with many freshwater fish of similar size.

For a group of 4–5 Ravnaki's halfbeaks, an aquarium of at least 120–130 litres is optimal. The design should balance open swimming areas with sheltered zones. These may include dense plant growth, interlaced driftwood, or other décor. Clean, flowing water rich in dissolved oxygen is essential for their long-term health. Moderate water flow is also beneficial. These conditions are achieved through regular tank maintenance and proper equipment function. Weekly partial water changes combined with siphoning organic waste are necessary.

In nature, the diet consists of small invertebrates such as insects and their larvae, crustaceans, worms and other zooplankton. They may occasionally eat small fish or fry. In the aquarium, provide high-protein food. The fish are known to feed in the upper and middle water layers, so floating foods or special live-food feeders should be used.

In the aquarium there is no seasonality to breeding, and fry appear every 4–6 weeks. These fish lack parental instinct, so young quickly become prey to adults if not removed in time. The fry are born large enough and can immediately feed on foods such as artemia, daphnia or mosquito larvae.

These fish rarely fall ill when kept in good conditions. Poor food quality, bad water quality and injuries are the main causes of disease. Often removing the cause is enough for the fish to recover on its own. In severe cases, medication may be needed.

When buying Ravnaki's halfbeak, choose active individuals that stay in the upper water layers and show interest in food. Inspect the fish carefully for jaw damage, as any injury to the 'beak' may prevent proper feeding. Avoid fish showing signs of emaciation, sunken belly or body coating, which often indicate stress from transport or bacterial infection. Since this species is sensitive to sudden changes in conditions, buy from trusted suppliers who guarantee proper acclimation after import. In the shop they should be kept in clean, well-aerated water without aggressive tank mates that could damage their fins.