Care
The Borneo Redline Halfbeak is known from heavily vegetated rainforest creeks. Here the water is very soft and acidic and is stained a tea colour by the tannins released from decaying plant matter. The aquarium must be biologically mature before these delicate top-dwellers are added. The tank should be sited in a quiet area and have as large a surface area as possible due to the fact this species can be rather skittish; indeed, it is very important that it is given adequate space so as not to damage the long, delicate mouth parts on the aquarium glass if it suddenly swims at speed. Tall tangles of driftwood and dense planting, including plenty of surface cover from floating species will help to feel these fish feel more secure. Filtration should be efficient but water movement gentle, and we'd suggest the use of aquarium peat as a filter medium to help emulate the natural water conditions. The addition of leaf litter would further help in this respect - dried Indian Almond leaves (Terminalia catappa) are ideal and are readily available. Much attention must be paid to water quality since H. tengah will not tolerate elevated nitrates or swings in water chemistry; small partial water changes should be carried out on a frequent basis. These fish are peaceful and best maintained in small groups of 6 or more. If tankmates are desired, they should be of similar size and temperament, and thrive under soft, acidic conditions. Good companions could include Chocolate Gouramis, Eirmotus octozona, Kuhli loaches (Pangio spp.), or Trigonostigma spp. Acclimatise very carefully, and ensure that the tank has tight fitting coverslides, as these fish are expert jumpers.
Feeding
Small meaty frozen foods such as daphnia, bloodworm, white mosquito larvae, vitamin-enriched brineshrimp etc. Feeds from the surface. Some specimens may also eventually accept dried foods.
Breeding
Unlike other species in the Hemirhamphodon genus, H. tengah is not a livebearer but instead an egg-layer. To breed successfully, this species requires acidic water with negligible hardness. The dominant male will display to and regularly mate with the females, with sub-dominant males keeping out of the way. A courting pair will hover under the water's surface, more or less parallel to each other, before the male swims jerkily alongside her, then swims backwards and around, so he is alongside her other flank. He will repeat this several times, moving around her in a loose rectangle. When ready to mate, the male stops alongside the female and tilts his body upwards and towards her. The pair bring their genital regions together and mate, before the male changes side again. It is unclear just how long the female waits before depositing the fertilised eggs into Java moss, peat, or spawning mops, but it is not thought to be immediate.
